Liquid crystal display apparatus

ABSTRACT

A display apparatus for executing display in accordance with an image signal, including, a display panel, a plurality of light-sources for illuminating the display panel, and a control circuit for controlling light-emission luminance of the light-sources. The light-emission luminance includes a first light-emission luminance and a second light-emission luminance, and the display panel includes a plurality of display areas, wherein each of the display areas corresponding to each of the light-sources. The control circuit controls switching timing between the first light-emission luminance and the second light-emission luminance of each of the light-sources in accordance with rewriting timing of the image signal concerned with each of the display areas.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/888,641, filed Jun. 26, 2001, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display apparatus using a liquidcrystal display device, an electroluminescence device, or the like. Moreparticularly, it relates to a display apparatus having a light-sourcethat is suitable for enhancing the luminance of the display screen witha high-efficiency and for making the luminance uniform on the displayscreen.

2. Description of the Related Art

The display apparatus, which uses the liquid crystal display device(which is also referred to as “liquid crystal display panel”), theelectroluminescence device (which, depending on a fluorescent materialused, is classified into an organic-family and an inorganic-family and,hereinafter, is referred to as “EL device”), a field emission device(which, hereinafter, is referred to as “FE device”), or the like,performs the image display. However, unlike the case of a Braun tube(which, hereinafter, is referred to as “CRT”, i.e., “cathode ray tube”),the display apparatus performs the image display under a condition thatthere is provided no space for 2-dimensionally scanning an electron beamon the back side of the display screen. Accordingly, as compared withthe CRT, these display apparatuses have characteristics of being thinnerand lighter-weighted, operating with a lower power consumption, and soon. These display apparatuses, in some cases, are referred to as “flatpanel displays” from the characteristics in their outward appearance.

From the above-described advantages over the CRT, the display apparatususing the liquid crystal display device, the EL device, the FE device,or the like is becoming widely prevalent in various types of uses insubstitution for a display apparatus using the CRT. In the background tothis situation, there exist the technical innovations such as anenhancement in the picture-quality of the liquid crystal display device,the EL device, or the like. Meanwhile, in recent years, the prevalenceof the multimedia and the Internet has been increasing a demand for themotion-frame picture display. As a result, in the display apparatususing the liquid crystal display device, improvements based on theliquid crystal material and the driving method are being made in orderto implement the motion-frame picture display. Being not limited to theliquid crystal display apparatus, however, in the display apparatusesreferred to as the flat panel displays, the implementation of a higherluminance for displaying an image comparable to that of the conventionalCRT has also become an important problem.

In order to obtain the image comparable to that of the conventional CRT,an impulse type light-emission is of absolute necessity. In the impulsetype light-emission, each pixel is scanned with an electron beam emittedfrom an electron gun, thereby causing a fluorescent substance in eachpixel to perform the light-emission.

In contrast to this, the liquid crystal display apparatus, for example,employs a hold type light-emission where a light-source unit including afluorescent lamp is used. On account of this, it has been regarded asdifficult for the display apparatus to implement the completemotion-frame picture display.

SUMMARY OF THE INVENTION

As the technology for solving the above-described problems related tothe liquid crystal display apparatus, the following has been reported: Amethod of making improvements in the liquid crystal material or in thedisplay mode of liquid crystal cells (i.e., a liquid crystal layersealed between the boards), and of using a directly-under typelight-source unit (i.e., a light-source structure where a plurality offluorescent lamps are located in a manner of being opposed to thedisplay screen of the liquid crystal display device) as thelight-source. FIG. 16 is a diagram for illustrating the result that thepresent inventor has obtained by analyzing an example of a lighting-upoperation method for the directly-under type light-source unit, theexample having been proposed for the motion-frame picture display. Thediagram illustrates the layout of the directly-under type light-sourceunit where 8 tube-shaped fluorescent lamps are located in a manner ofbeing opposed to the display screen (the dashed-line frame), and, as theluminance waveforms, timings of the respective lighting-up startingtimes for the respective lamps. The luminance waveforms illustrated inFIG. 16 indicate that the luminances are enhanced when the luminancewaveforms become convex in an upward direction in the drawing. Asclearly seen from FIG. 16, the lighting-up starting times for therespective fluorescent tubes are shifted in sequence from the startingtimes located on the upper side to the starting times located on thelower side. This sequential lighting-up operation, which is synchronizedwith a scanning period of an image display signal, has been repeated onthe basis of a 1-frame image display time-period (i.e., a time-periodduring which the display signal is transferred to all the pixels on thedisplay screen). (Refer to “Liquid Crystal”, Vol. 3, No. 2 (1999), pp.99-106).

On the other hand, there exists a technology by which the luminance ofthe light-source is modulated in correspondence with the scene of amotion-frame picture signal transmitted to the liquid crystal displayapparatus. This technology allows the following operation: Reading outmaximum luminance data, minimum luminance data, and average luminancedata of the display signal transmitted to the liquid crystal displayapparatus for each image included in the motion-frame picture signal,and, in correspondence with these data, controlling an electric current(hereinafter, referred to as “lamp current”) that is to be fed to thelight-source. Assuming that the lamp current is usually equal to areference current (e.g., 4.5 mA), in the case of an image that is brightas a whole, the lamp current is set to be higher (e.g., 8 mA) than thereference current during a certain time-period, afterwards beingrestored back to the reference current. Conversely, in the case of animage that is dark as a whole, the lamp current is set to be lower(e.g., 1.5 mA) than the reference current. (Refer to “NikkeiElectronics”, No. 757, Sep. 15, 1999, pp. 139-146).

This setting, in the former case (i.e., the image that is bright as awhole), feeds to the light-source the lamp current that is higher thanthe reference current, thereby resulting in a temperature increase inthe light-source which is larger by the amount of feeding the higherlamp current. In the case of the fluorescent lamps, the temperatureincrease raises the mercury (Hg) vapor pressures inside the fluorescentlamps, thereby increasing the number of mercury atoms (i.e., mercuryvapor quantity) inside the fluorescent lamps. Meanwhile, if there existsurplus mercury atoms inside the fluorescent lamps, the surplus mercuryatoms heighten a probability that ultraviolet rays generated inside thefluorescent lamps by the collision between the mercury atoms and theelectrons are absorbed into the mercury atoms, eventually decreasing theluminances of the fluorescent lamps themselves. In order to avoid thisinfluence, after having set the lamp current to be higher than theabove-described reference current during the above-describedtime-period, the lamp current is restored back to the reference currentbefore the mercury vapor pressures inside the fluorescent lamps arealtered. Changing the lamp current in this way makes the luminances ofthe fluorescent lamps higher than those of the fluorescent lamps at thetime when the reference current is fed thereto. Also, in the latter case(i.e., the image that is dark as a whole), if the luminance of thelight-source is high, it becomes required to suppress a slight leakageof the light from a pixel displaying black or a color close thereto. Onthe screen that is dark as a whole, even in a pixel thelight-transmittance of which is set to be the highest within the screen,the absolute quantity of the light to be transmitted is small. Onaccount of this, the lamp current is set to be lower than the referencecurrent, thereby suppressing the luminance of the light-source so as tothrottle the leakage of the light from the pixel displaying black or thecolor close thereto, and at the same time reducing the power consumptionin the light-source.

From the combination of these two technologies, the dynamic range (i.e.,the ratio of the maximum luminance/the minimum luminance) of theluminance in an image viewed in all the motion-frame pictures can beexpanded up to 2.8 times as wide as the conventional dynamic range.Moreover, the contrast ratio thereof can be expanded up to 400˜500:1,which is more than 2 times as high as that of the conventional liquidcrystal display apparatus.

When the above-described technology of performing in sequence thelighting-up operation for the directly-under type light-source unit isexecuted in the liquid crystal display apparatus, for example, thenumber of the fluorescent lamps mounted on the directly-under typelight-source unit is increased. This attempt shortens the light-emissiontimes of the respective fluorescent lamps which are occupied during a1-period (which is equivalent to the amount of 1 frame) lighting-upoperation time-period. This eventually decreases the luminanceefficiency of the directly-under type light-source unit as a whole.

Also, if the electric powers applied to the respective fluorescent lampsare increased in order to heighten the luminance of a displayed image,the resultant fever by the fluorescent lamps locally heats the liquidcrystal cells, thereby reducing the uniformity as well.

The image display in the liquid crystal display apparatus is executed asfollows: Liquid crystal molecules that are sealed into the liquidcrystal cells of the liquid crystal display device mounted on thedisplay apparatus are orientated in a direction corresponding to theimage information (i.e., an electric field applied to the liquid crystalcells) so as to set the light-transmittances of the liquid crystal cellsto be a desired value. For this purpose, it is desirable to maintain theviscosity within the liquid crystal cells at a proper value so that theliquid crystal molecules in the liquid crystal cells are securelyorientated in the direction corresponding to the image information.Here, in some cases, a viscosity-increasing agent or aviscosity-decreasing agent, together with the liquid crystal molecules,is sealed into the liquid crystal cells. If, however, the temperaturesof the liquid crystal cells are increased locally, the viscosity islowered at this section. On account of this, the directions of a portionof the liquid crystal cells become random (equal-directing of the liquidcrystal layer).

Consequently, only the liquid crystal cells at this section exhibit thelight-transmittances not corresponding to the electric field applied tothe liquid crystal molecules. This condition makes it difficult toraise, up to 300 cd/m² or higher, the display luminance by a transverseelectric-field type liquid crystal display apparatus.

Also, when the above-described technology of adjusting the luminance ofthe light-source for each image included in the motion-frame picturesignal is executed toward the liquid crystal display apparatus, from apractical standpoint, it is difficult to set the timing with which thelamp current, which is fed to the light-source at the time of displayingthe image that is bright as a whole, is lowered from the value higherthan the above-described reference current down to the referencecurrent. As having been described earlier, in order to make theluminance of the light-source higher than the value at the time when thereference current is fed to the light-source, the lamp current that hasbeen once set to be higher than the reference current must be restoredback to the reference current before the mercury vapor pressures insidethe fluorescent lamps are altered. However, the timing with which thelamp current is switched in this manner cannot help being setempirically in accordance with, for example, the correlation betweenmeasurement data of the temperature increase in the light-source (i.e.,the fluorescent lamps) and the luminance of the light-source. Also, ifthe usage conditions for the display apparatus the examples of whichinclude even a difference in the room temperature or the like should betaken into consideration, it is extremely difficult to set the timingwith which the lamp current is switched. Furthermore, in thistechnology, since the light-source luminance at each image displaypoint-in-time is changed in response to the brightness of each image,the contrast ratio for each image remains at an order that theconventional liquid crystal display apparatus makes it possible toaccomplish. This, in other words, means the following: Even if thistechnology is applied to the liquid crystal display apparatus, whendisplaying an image the brightness of which remains almost unchangedover a certain fixed time-period (i.e., a time-period during whichdisplay data of a plurality of frames is transferred to the liquidcrystal display apparatus), it is difficult to enhance the contrastratio thereof.

It is an object of the present invention to provide a liquid crystaldisplay apparatus and a control method therefor, the liquid crystaldisplay apparatus enhancing the luminance of a displayed image with ahigh-efficiency and suppressing the heat-liberation of the light-source.

Also, it is another object of the present invention to provide a liquidcrystal display apparatus that improves a blur in a motion-framepicture, and a control method therefor.

Also, it is still another object of the present invention to provide aliquid crystal display apparatus that enhances the contrast ratio, and acontrol method therefor.

In order to accomplish the above-described objects, in the presentinvention, the following configuration is employed: In a liquid crystaldisplay apparatus that includes a liquid crystal panel and alight-source provided onto the liquid crystal panel for illuminating thepanel, the light-source has a period constituted by a 1st light-emissionluminance and a 2nd light-emission luminance, the time ratio of the 1stlight-emission luminance and that of the 2nd light-emission luminanceduring the period being changed in accordance with display data suppliedfrom the outside.

Here, the 1st light-emission luminance is higher than the 2ndlight-emission luminance. As one example thereof, the time ratio of the1st light-emission luminance during the period is set to be 60% orsmaller when the display data is of motion-frame pictures, and is set tobe 60% or larger when the display data is of freeze-frame pictures.Also, the 2nd light-emission luminance is set to be substantially 0,which is intended to enhance the reproducibility at the time when theafterimage and the luminance of the 2nd light-emission luminance arelow.

Also, as one example of the controlling circuit configuration, thecontrolling circuit includes the following components: A data storingunit for storing the display data at least by the amount of 1 frame, adata comparing unit for comparing corresponding pixels between thedisplay data stored in the data storing unit and the display data to beinputted, and a pulse controlling unit that, in correspondence with thecomparison result by the data comparing unit, outputs a signal forcontrolling the time ratio of the 1st light-emission luminance duringthe period.

Also, the present invention includes a liquid crystal display apparatuswhere the comparison pixels compared by the data comparing unit have adistribution of being concentrated in a proximity to the center of adisplay unit of the above-described liquid crystal panel. Here, theproximity to the display unit may also be a region determined inadvance. This region may also be contained within a fixed-length ofdistance from a predetermined pixel.

Also, in order to make the liquid crystal display apparatus correspondto the plurality of light-sources, the controlling circuit is configuredas follows: The controlling circuit define to display panel withcorresponding to each source light, and starting time of above-mentionedfirst luminous and second luminous luminance is organized that is ableto change with according to display data supplying from outside withaccording to display data with each fields.

As another example of the controlling circuit configuration, thecontrolling circuit includes the following components: A luminance datageneration controlling unit for generating luminance data from therespective image data of R, G, and B, a luminance distribution detectioncontrolling unit that, from the generated luminance data, detects aluminance distribution state for the input image data by the amount of 1frame, a folded-line point tone controlling unit for controlling a tonecharacteristic in accordance with the luminance distribution detectionresult, a backlight light-dimmer controlling unit for performing alight-dimmer control over a backlight in accordance with the luminancedistribution detection result, and a blink backlight controlling unitfor controlling a light-emission timing of the backlight for the displaydata by the amount of 1 frame.

Also, as still another example of the controlling circuit configuration,it is also allowable to employ a configuration that simultaneously hasboth of the configurations presented by the above-described twoexamples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for illustrating a liquid crystal displayapparatus to which the present invention is applied;

FIG. 2 are diagrams for illustrating luminance waveforms of alight-source and so on in the liquid crystal display apparatus to whichthe present invention is applied;

FIGS. 3A and 3B are diagrams for illustrating the structure of a liquidcrystal display apparatus using a sidelight type light-source unit;

FIGS. 4A and 4B are diagrams for illustrating the structure of a liquidcrystal display apparatus using a directly-under type light-source unit;

FIGS. 5A and 5B are diagrams for illustrating the in-tube temperature ofa cold-cathode ray tube and the luminance characteristic toward a fedcurrent;

FIG. 6 is a diagram for illustrating the luminance response by thelight-source unit according to the present invention;

FIGS. 7A and 7B are diagrams for illustrating the elapsed-time change ofthe display luminance of a liquid crystal display apparatus where acold-cathode ray tube is employed as the light-source, and theelapsed-time change of the cold-cathode ray tube temperature;

FIG. 8 is a diagram for illustrating an embodiment of a controllingcircuit for executing a blinking lighting-up of the light-sourceaccording to the present invention;

FIG. 9 is a diagram for illustrating an embodiment of the setting of ablinking lighting-up ratio of the light-source according to the presentinvention;

FIG. 10 is a diagram for illustrating an embodiment of the setting ofthe blinking lighting-up ratio of the light-source according to thepresent invention;

FIGS. 11A, 11B, and 11C are diagrams for illustrating an embodiment ofthe setting of a blinking lighting-up period of the light-sourceaccording to the present invention;

FIG. 12 is a diagram for illustrating an embodiment of the setting of apausing time-period in the blinking lighting-up of the light-sourceaccording to the present invention;

FIGS. 13A and 13B are diagrams for illustrating an embodiment of thesidelight type light-source unit according to the present invention;

FIGS. 14A and 14B are diagrams for illustrating the structure of theliquid crystal display apparatus (i.e., a transverse electric-field modeliquid crystal display apparatus) using the sidelight type light-sourceunit according to the present invention;

FIG. 15 is a diagram for illustrating the layout of an inverterapparatus used in the liquid crystal display apparatus illustrated inFIGS. 13A, 13B;

FIG. 16 is a diagram for illustrating the result that the presentinventor has obtained by analyzing the lighting-up operation method forthe directly-under type light-source unit that belongs to the prior art;

FIG. 17 is a diagram for illustrating the configuration of a controllingcircuit for the sidelight type light-source unit according to thepresent invention;

FIG. 18 is a diagram for illustrating an example of a switchingcontrolling circuit 25 illustrated in FIG. 17;

FIG. 19 is a timing diagram of a light-source lighting-up signal BLgenerated by the switching controlling circuit 25 illustrated in FIG.18;

FIGS. 20A and 20B are comparison diagrams where the conventional holdtype light-emission is compared with an impulse type light-emissionaccording to the present invention;

FIGS. 21A and 21B are diagrams for illustrating an embodiment of adetection point of the data comparison in the present invention;

FIG. 22 is a diagram for illustrating an embodiment of the switchingcontrolling circuit 25 illustrated in FIG. 17;

FIG. 23 is a diagram for illustrating a dividing method for a displayscreen for explaining the switching controlling circuit 25 illustratedin FIG. 22;

FIG. 24 is a timing diagram of a light-source lighting-up signal BLgenerated by the switching controlling circuit 25 illustrated in FIG.22;

FIG. 25 is a diagram for illustrating the configuration of a controllingcircuit for the directly-under type light-source unit according to thepresent invention;

FIG. 26 is a diagram for illustrating an embodiment of the switchingcontrolling circuit 25 illustrated in FIG. 25;

FIG. 27 is a timing diagram of light-source lighting-up signals BL 1 toBL 4 generated by the switching controlling circuit 25 illustrated inFIG. 26;

FIG. 28 is a diagram for illustrating a switching controlling circuit 25for implementing a light-source lighting-up control in correspondencewith the display luminance of a displayed image according to the presentinvention;

FIG. 29 is a timing diagram of a light-source lighting-up signal BLgenerated by the switching controlling circuit 25 illustrated in FIG.28;

FIG. 30 is a diagram for illustrating the configuration of a lighting-upmethod instructing circuit 60 according to the present invention;

FIG. 31 is a schematic configuration diagram of a liquid crystal displaymodule according to another embodiment of the present invention;

FIG. 32 is a schematic configuration diagram of a TCON board implementedon the back surface of the liquid crystal display module according tothe present invention;

FIG. 33 is a schematic configuration diagram of the internal function ofLSIs mounted on the TCON board according to the present invention;

FIG. 34 is a specification diagram of image data conversion (i.e.,low-voltage differential→TTL, and TTL→low-voltage differential)input/output signals according to the present invention;

FIG. 35 is a schematic timing diagram of the operation of a frame memorycontrolling unit according to the present invention;

FIG. 36 is a timing diagram of a driver interface according to thepresent invention;

FIG. 37 is a timing diagram of a digital backlight light-dimmer signalaccording to the present invention;

FIG. 38 is a conceptual diagram of the operation of a luminance datageneration controlling unit according to the present invention;

FIG. 39 is a schematic configuration diagram of a luminance distributiondetection controlling unit according to the present invention;

FIG. 40 is a state transition diagram for illustrating the operation ofa luminance distribution detecting unit according to the presentinvention;

FIG. 41 is a schematic diagram for showing a luminance distributiondetection result obtained by the luminance distribution detectioncontrolling unit according to the present invention, and anarithmetic-calculation formula for calculating a luminance average valuefrom the detection result;

FIG. 42 is a state transition diagram for illustrating the operation ofanother embodiment that differs from the embodiment illustrated in FIG.40 of the luminance distribution detecting unit according to the presentinvention;

FIG. 43 is a schematic diagram for showing a luminance distributiondetection result obtained by another embodiment that differs from theembodiment illustrated in FIG. 41 of the luminance distributiondetection controlling unit according to the present invention, and anarithmetic-calculation formula for calculating a luminance average valuefrom the detection result;

FIG. 44 is a diagram for illustrating the tone control by a folded-linepoint tone controlling unit according to the present invention;

FIG. 45 is a schematic configuration diagram of the folded-line pointtone controlling unit according to the present invention;

FIG. 46 is a diagram for illustrating the tone control by anotherembodiment that differs from the embodiment illustrated in FIG. 44 ofthe folded-line point tone controlling unit according to the presentinvention;

FIG. 47 is a schematic configuration diagram of another embodiment thatdiffers from the embodiment illustrated in FIG. 45 of the folded-linepoint tone controlling unit according to the present invention;

FIG. 48 illustrates an example of a light-dimmer characteristic diagramin an inverter board according to the present invention;

FIG. 49 illustrates an example of the luminance control and themotion-frame picture's blur improving control by a backlightlight-dimmer controlling unit and a blink controlling unit according tothe present invention;

FIG. 50 illustrates an example of the image judgement based on theluminance distribution detection data according to the presentinvention;

FIG. 51 illustrates an example of a state transition diagram of thelight-dimmer control in accordance with an image judging condition'sexample according to the present invention;

FIG. 52 illustrates an example of the luminance control and themotion-frame picture's blur improving control by another embodimentsthat differs from the embodiments illustrated in FIG. 49 of thebacklight light-dimmer controlling unit and the blink controlling unitaccording to the present invention;

FIG. 53 illustrates an example of the luminance control and themotion-frame picture's blur improving control by another embodimentsthat differs from the embodiments illustrated in FIGS. 49 and 52 of thebacklight light-dimmer controlling unit and the blink controlling unitaccording to the present invention;

FIG. 54 illustrates an example of the luminance control and themotion-frame picture's blur improving control by another embodimentsthat differs from the embodiments illustrated in FIGS. 49, 52 and 53 ofthe backlight light-dimmer controlling unit and the blink controllingunit according to the present invention; and

FIG. 55 illustrates an example of the luminance control and themotion-frame picture's blur improving control by another embodimentsthat differs from the embodiments illustrated in FIGS. 49, 52, 53 and 54of the backlight light-dimmer controlling unit and the blink controllingunit according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention includes a panel on which a plurality of pixelsare located, a light-source for visualizing an image displayed on theplurality of pixels, and a controlling circuit for controlling thelight-source. Here, during a 1st time-period, the controlling circuitfeeds the light-source an electric current having a 1st intensity.During a 2nd time-period, the controlling circuit feeds the light-sourcean electric current having a 2nd intensity (which differs from the 1stintensity). Also, the controlling circuit repeats the 1st time-periodand the 2nd time-period periodically. Furthermore, the controllingcircuit controls the light-source so that the intensity of a lightemitted from the light-source in this period (i.e., an integrated valueobtained by integrating the luminance of the light during this period)will become higher than an integrated value of the luminance in the casewhere the light-source is lit up by a rating electric current during thesame time-period. Incidentally, concerning the integrated value of theluminance in the case where the light-source is lit up by the ratingcurrent, the luminance being in a stable state in about 30 minutes afterthe lighting-up has been employed as the target to be integrated.

Also, in the case where the display apparatus is a liquid crystaldisplay apparatus, the panel includes a pair of boards (at least one ofwhich has a light-transmittance that is large enough to permit the lightfrom the light-source to pass) located in such a manner as to be opposedto each other, and a liquid crystal layer (i.e., liquid crystalmolecules, or the molecules including an additive agent such as aviscosity-decreasing agent) sealed between the pair of boards. Moreover,on at least one of the pair of boards, there are provided electrodesincluded in the pixels and signal lines for transferring imageinformation to the electrodes. The panel configured in this manner isreferred to as “liquid crystal display panel” or “liquid crystal displayelement”. In the light-source, a fluorescent lamp or an optical element(e.g., a light-guiding plate) connected optically to the fluorescentlamp is located on at least one plane of the panel in a manner of beingopposed thereto. In recent years, there has been also proposed alight-source using a light-emitting element array where, instead of thefluorescent lamp, a plurality of light-emitting elements are locatedalong the panel. The present invention is applicable to a matrix typedisplay apparatus. On account of this, the present invention is alsoapplicable to a plasma display apparatus.

In the display apparatus according to the present invention, thelarge-or-small relationship between the 1st and the 2nd electriccurrents that are fed to the light-source is not particularly specified.However, as is the case with the conventional case, considering the caseas well where the display apparatus is utilized under a condition oflighting up the light-source continuously, it is desirable to set the2nd electric current to be smaller as compared with the 1st electriccurrent.

Incidentally, in the liquid crystal display element, the luminance of animage to be displayed is calculated from an image-signal transferred tothe display apparatus, and then the 1st and the 2nd current values andthe time sharing of the 1st and the 2nd time-periods may be adjusted inagreement with the calculated luminance (a viewpoint 1). In particular,with respect to image data the luminance or the contrast of which neednot be enhanced, the value of, especially, the larger one out of the 1stand the 2nd currents is suppressed, thereby saving the powerconsumption. In this case, even if the intensity of the light emittedfrom the light-source in the period (i.e., the integrated value obtainedby integrating the luminance of the light during the period) becomeslower than the integrated value of the luminance in the case where thelight-source is lit up by the rating current during the sametime-period, this situation presents no problem.

Hereinafter, the explanation will be given concerning the concrete modesof the present invention, referring to the drawings related therewith.

In the drawings that will be referred to in the following explanation,the configuration components having the same function are designated bythe same reference numerals, and the repeated explanation thereof willbe omitted.

FIG. 1 is a schematic diagram for illustrating a liquid crystal displayapparatus on which a liquid crystal display module according to thepresent invention is mounted. In FIG. 1, the reference numerals denotethe following components, respectively: 8 a fluorescent lamp, 20 adirect voltage source input terminal, 21 an inverter circuit, 23 alight-dimmer circuit, 25 a switching controlling circuit, 27 a liquidcrystal panel, 28 the liquid crystal display module, 29 a televisioninput terminal, 30 a video input terminal, 31 an S input terminal, 32 ananalogue PC input terminal, 33 a digital PC input terminal, 34 ananalogue image processing controlling unit, 35 a digital imageprocessing controlling unit, and 36 the liquid crystal displayapparatus.

In FIG. 1, the liquid crystal display apparatus 36 mainly allows amotion-frame picture from, as image inputs, the television inputterminal 29, the video input terminal 30, the S input terminal 31, andso on, and mainly allows a freeze-frame picture from the analogue PCinput terminal 32, the digital PC input terminal 33, and so on. Theanalogue image processing controlling unit 34 subjects inputted analogueimage data to a luminance/color signal separation processing, ananalogue/digital conversion processing, and so on, then outputting, asdigital image data, the data to the digital image processing controllingunit 35. The digital image processing controlling unit 35 subjects thedigital image data to an interlace/non-interlace conversion processing,an expansion processing, and so on, then outputting the data to theliquid crystal display module 28. In the liquid crystal display module28, the inputted digital image data (DATA) is inputted into theswitching controlling circuit 25 as well as into the liquid crystalpanel 27. The switching controlling circuit 25 detects the state of thisinputted digital image data (DATA). In addition, the switchingcontrolling circuit 25 outputs a detection signal, i.e., the detectionresult, to the light-dimmer circuit 23. In accordance with the state ofthis detection signal, the light-dimmer circuit 23 outputs to theinverter circuit 21 a light-dimmer controlling signal for obtaining anexcellent display state. This allows the light-dimmer circuit 23 toperform a light-source control over the fluorescent lamp 8.

Hereinafter, the explanation will be given in sequence concerning thedetails of the respective components.

FIGS. 3A and 4A are cross-sectional views for conceptually illustratingthe structures of the liquid crystal panel. FIGS. 3B and 4B areperspective vies for illustrating a light-source unit fixed onto theliquid crystal display apparatus. In any one of the drawings, the liquidcrystal panel has a liquid crystal display element and a light-sourceunit 10 where the fluorescent lamp 8 is mounted. Here, the liquidcrystal display element includes a pair of boards 3 the respectiveprincipal planes of which are located in a manner of being opposed toeach other, and a liquid crystal layer 2 (i.e., liquid crystalmolecules, or a mixture of the molecules and a viscosity-decreasingagent or the like are sealed) sandwiched between the pair of boards. InFIGS. 3A and 4A, on the principal planes of the boards 3, sheetpolarizers 1 are provided on the sides opposite to the liquid crystallayer 2. Also, on at least one of the pair of boards 3, a plurality ofpixels (not illustrated) are located in a 2-dimensional manner on theprincipal plane on the side of the liquid crystal layer 2. In the panelillustrated in either of FIGS. 3A and 4A, the user can see an image fromthe above in the drawings through the principal planes of the boards 3.

The liquid crystal panel illustrated in FIGS. 3A and 3B is referred toas “sidelight type” (or “edgelight type”) from the location of thefluorescent lamp 8 in the light-source unit 10. The light-source unit 10includes the following components: A light-guiding plate 11 having aquadrilateral-shaped upper plane located in a manner of being opposed toa lower plane of the above-described liquid crystal display element, thetube-shaped fluorescent lamps 8 located along at least one side plane(i.e., one side of the quadrilateral) of the light-guiding plate, areflector 7 by which a light emitted from the fluorescent lamp 8 ontothe opposite side of the light-guiding plate is launched into the sideplane of the light-guiding plate, and a reflection film 9 by which alight propagating inside the light-guiding plate down toward its lowerplane is caused to be reflected up toward its upper plane and is causedto illuminate the lower plane of the liquid crystal display element.Between the upper plane of the light-guiding plate 11 and the lowerplane of the liquid crystal display element, there is located an opticalsheet group 4 including a pair of diffusion films 6 and a prism sheet 5sandwiched therebetween. In the sidelight type liquid crystal panel, thelower plane of the liquid crystal display element is located in such amanner that the lower plane is opposed not to the fluorescent lamp 8 butto the upper plane of the light-guiding plate 11 illustrated in FIG. 3B.

In contrast to this, the liquid crystal panel illustrated in FIGS. 4Aand 4B is referred to as “directly-under type”. This is named after thelocation that a plurality of fluorescent lamps 8 in the light-sourceunit 10 are located in a manner of being opposed to the lower plane ofthe liquid crystal display element (i.e., directly under the liquidcrystal panel as illustrated in FIG. 4A). In the light-source unit 10used in the directly-under type liquid crystal panel, reflectors 7 arelocated so that lights emitted from the fluorescent lamps 8 down towardthe lower side in the drawing are reflected so as to illuminate theupper side in the drawing (i.e., the lower plane of the liquid crystaldisplay element). For this purpose, there are formed ups-and-downs foreliminating variations in the light intensities in the plurality offluorescent lamps 8 and the clearances therebetween. As is the case withthe sidelight type panel, an optical sheet group 4 is located betweenthe light-source unit 10 and the liquid crystal display element.However, the diffusion sheets 6 located on the side of the light-sourceunit 10 in the sidelight type optical sheet group 4 have been replacedby a diffusion plate 6 a. In the diffusion plate 6 a, there is formed anoptical pattern for eliminating the above-described variations in thelight intensities in the plurality of fluorescent lamps 8 and theclearances therebetween.

Additionally, the detailed explanation of the sidelight type liquidcrystal panel and that of the directly-under type liquid crystal panelhave been given in, e.g., JP-A-7-281185 and JP-A-5-257142, respectively.

In the above-described liquid crystal panels, increasing or decreasingan applied electric field to the liquid crystal layer 2 sets thelight-transmittance, thus displaying an image. For example, in a TFT(i.e., thin film transistor)-driven liquid crystal display apparatus(active matrix type) of the TN type or the vertical orientation typewhere the liquid crystal molecules are orientated at a twist angle ofaround 90°, or in a time-division-driven liquid crystal panel (passivematrix type) of the STN type where the molecules are orientated at atwist angle of 200° to 260°, with an increase in the applied electricfield to the liquid crystal layer 2, the light-transmittance changesfrom its maximum value (white image) to its minimum value (black image).

On the other hand, in a TFT-driven liquid crystal panel referred to asthe transverse electric-field type where the electric field to beapplied to the liquid crystal layer 2 is applied in the direction alongthe board plane, with an increase in the applied electric field to theliquid crystal layer 2, the light-transmittance changes from its minimumvalue (black image) to its maximum value (white image).

In the case of the TN type or the vertical orientation type TFT-drivenliquid crystal panel, as the value of Δnd which is the product of arefractive-index anisotropy Δn of the liquid crystal layer 2 and a cellgap (i.e., thickness of the liquid crystal layer 2) d, the range of 0.2μm to 0.6 μm is desirable in order to make the contrast ratio and thebrightness compatible with each other. As the value of Δnd in the STNtype liquid crystal panel, the range of 0.5 μm to 1.2 μm is preferable.As the value of Δnd in the transverse electric-field type TFT-drivenliquid crystal panel, the range of 0.2 μm to 0.5 μm is preferable.

Next, in accordance with the above-described viewpoint, the explanationwill be given below concerning overviews of the aspects of the presentinvention in the liquid crystal panels configured as described above.

FIG. 2 are diagrams for illustrating a synchronization signal (i.e., atransferring timing of image information), an image display signal, alighting-up signal of the light-source, and a luminance waveform of alight emitted from the light-source unit at the time when the presentinvention based on the viewpoint 1 is carried out toward the liquidcrystal display apparatus. The light-source lighting-up signal isrepresented as a waveform indicating the following operation: The 1stelectric current i^(I) is fed to the light-source during a time ofΔt^(I) (i.e., the 1st time-period), and then the 2nd electric currenti^(II) smaller than the 1st electric current is fed to the light-sourceduring a time of Δt^(II) (i.e., the 2nd time-period), and an operationperiod of Δt^(I)+Δt^(II), i.e., a summation of these two times, isrepeated. In this example, Δt^(I) and Δt^(II) have been set to be equalto each other. Namely, the electric currents are fed to the light-sourcewith the duty of 50%, and the value of the 2nd electric current i^(II)is suppressed down to substantially 0 mA. Accordingly, assuming that aconstant electric current is fed to the light-source with an electricpower that the light-source consumes in the above-described operationperiod, it turns out that the electric current value is illustrated asan intermediate value i^(const) between the 1st electric current and the2nd electric current.

Furthermore, the luminance waveform of the light-source makes itpossible to predict that the luminance corresponding to i^(const) willbe equivalent to an intermediate value I^(const) (a dashed line) betweena luminance I^(I) corresponding to the 1st electric current (i.e., avalue that the luminance reaches by the feeding of the 1st electriccurrent during the predetermined time) and a luminance I^(II)corresponding to the 2nd electric current (i.e., a value that theluminance reaches by the feeding of the 2nd electric current during thepredetermined time). However, the continuous feeding of the currenti^(const) in a time equivalent to the plurality of operation periodsgradually raises the light-source temperature, thereby resulting in agradual increase in the light loss inside the light-source. On accountof this, actually, the luminance of the light-source exhibits a valueI^(const) (a solid line) that is lower than I^(const) (the dashed line).Also, the temperature increase in the light-source with the lapse oftime gradually expands, from ΔI¹ to Δi², the difference betweenI^(const) (the dashed line) and I^(const′) (the solid line).

In contrast to this, if the time of Δt^(I) during which the 1st currenti^(I) is fed to the light-source is set to be shorter than a turnaroundtime during which the temperature increase in the light-source caused bythe 1st current i^(I) reaches a certain value, it becomes possible toextract, without the light loss inside the light-source, the light ofthe luminance corresponding to the 1st current i^(I). FIGS. 5A and 5Brelate to a cold-cathode ray tube employed as one example of thelight-source. FIG. 5A indicates the relationship between the in-tubetemperature (which can be regarded as being equivalent to the in-tubemercury vapor pressure as well) and the luminance. FIG. 5B indicates therelationship between the luminance and a current fed to a pair ofelectrodes provided in the cold-cathode ray tube. The luminance of thecold-cathode ray tube depends on the in-tube mercury vapor pressure, inother words, the quantity of the mercury gas existing inside the tube.When the mercury gas quantity is smaller than a certain value (which, inthis example, is equal to 4.7 Pa in terms of the mercury vaporpressure), an increase in the mercury gas quantity brings about anincrease in the in-tube temperature, thereby raising the luminance ofthe cold-cathode ray tube itself as well. If, however, the mercury gasquantity exceeds the certain value, the mercury gas gradually absorbsthe light generated inside the tube, eventually resulting in a decreasein the luminance of the cold-cathode ray tube as well. The tendency likethis, being not limited to the cold-cathode ray tube and the mercurygas, can be recognized as long as the tube sphere contains an excitationmaterial therein. The phenomenon similar to that in the cold-cathode raytube occurs also in, for example, a xenon lamp.

Also, the mercury vapor pressure inside the cold-cathode ray tube can beregarded as being equivalent to the temperature inside the cold-cathoderay tube as well. Moreover, the temperature inside the cold-cathode raytube is raised in response to the current fed between the pair ofelectrodes provided in the cold-cathode ray tube. Consequently, whencontinuously feeding the current to the cold-cathode ray tube, the risein the luminance is saturated in response to the rise in the currentvalue, and thus the luminance will be saturated at a certain value(Refer to FIG. 5B).

However, as illustrated in the luminance waveform of the light-source inthe 1st time-period Δt^(I) in FIG. 2, the feeding of the current i^(I)to the cold-cathode ray tube raises its luminance gradually. This factclearly shows that the rise in the in-tube temperature at the time offeeding a predetermined current to the cold-cathode ray tube occurs witha certain accompanying delay with respect to a feeding startingpoint-in-time of the current i^(I). Moreover, considering a rewritingperiod of the image data signal in the liquid crystal display apparatus,it is desirable to set the above-described operation period of thelight-source to be smaller than this period. This period is equal to,e.g., 16.7 ms (ms=milliseconds) at 60 Hz, and 8.4 ms at 120 Hz (thesevalues are preferable for the motion-frame picture display). It isdesirable to set the above-described operation period of thelight-source to be smaller than these periods. However, by setting theabove-described time sharing of the 1st and the 2nd time-periods and theabove-described 1st and the 2nd currents in correspondence with thisoperation period, it is possible to reduce the influence of theabove-described temperature rise. From the catalogue of the respectivecold-cathode ray tubes referred to earlier, when lighting up thecold-cathode ray tube continuously with the rating current thereof (anexample of its value: 6 mA), the following findings can be obtaineddepending on the surrounding temperature of the cold-cathode ray tube:

(1) At a surrounding temperature of 40° C., the luminance is saturatedin about 150 seconds from the starting of the lighting-up, and adecrease in the luminance is unobserved even after the lapse of 200seconds.

(2) At a surrounding temperature of 60° C., the luminance exhibits itsmaximum value in about 15 seconds from the starting of the lighting-up,and after that, the luminance is decreased slowly and attains to 90% ofits maximum value after the lapse of 200 seconds.

(3) At a surrounding temperature of 80° C., the luminance exhibits itsmaximum value in about 10 seconds from the starting of the lighting-up,and for about 10 seconds after that, the luminance is rapidly decreaseddown to 80% of its maximum value, and thereinafter, the luminance isdecreased slowly until after the lapse of 200 seconds from the startingof the lighting-up.

Based on these findings, the present inventor has thought of thefollowing idea and has confirmed its effect: Even if the 1st current hasbeen set to be substantially 2 times as large as the rating current ofthe cold-cathode ray tube, the value of the 2nd current, which is set tobe smaller as compared with the 1st current, and its feeding time (i.e.,the 2nd time-period) are adjusted. This operation makes it possible toprevent the temperature rise in the cold-cathode ray tube.

Meanwhile, in the 2nd time-period, since the 2nd current smaller thanthe 1st current is fed to the light-source, the luminance of thelight-source is decreased. However, when seen from the point-of-view ofa luminance of the light that has passed through the liquid crystaldisplay element (hereinafter, this luminance is referred to as “panelluminance”), the influence of the luminance decrease in the 2ndtime-period is unexpectedly small. Having made the comparison with theuse of an integrated value of the panel luminance in the above-describedoperation period (the duty: 50%) by the amount of Δt^(I)+Δt^(II) at thetime when the 2nd current is set to be 0 mA, concerning afterglow of thelight-source which occur in the 2nd time-period, the following findingshave been obtained experimentally (Refer to FIG. 6):

(4) When a pixel of the liquid crystal display element iswhite-displayed (i.e., an image-signal that makes thelight-transmittance of this pixel its maximum value is sent to thispixel), the attenuation of the light that has passed through the pixelis smaller than having been expected. Moreover, an integrated value ofthe display luminance has become larger than the value at the time whenthe light-source is continuously lit up with the same electric power inthe above-described operation period.

(5) When a pixel of the liquid crystal display element isblack-displayed (i.e., an image-signal that makes thelight-transmittance of this pixel its minimum value is sent to thispixel), the attenuation of the light that has passed through the pixelis sufficiently large. Moreover, an integrated value of the displayluminance has been suppressed down to about one-half of the value at thetime when the light-source is continuously lit up with the same electricpower in the above-described operation period.

Being not limited to the liquid crystal display apparatus, the maximumluminance required for the display apparatus turns out to become theluminance of a pixel displayed brightest (i.e., in white) out of aplurality of pixels. In the other pixels, in particular, in a pixeldisplayed darkest (i.e., in black) or a pixel displayed in a tone closethereto (i.e., in dark gray), if the display luminances thereof areincreased, the entire display screen becomes a whitish image. The userof the liquid crystal display apparatus regards this whitish image aslooking inferior to the image by the CRT.

However, the above-described findings (4) and (5) that the presentinventor et al. have obtained experimentally have proved the following:In comparison with the conventional method of feeding the currentcontinuously, as described above, the modulation of the current fed tothe light-source with the predetermined duty makes it possible toenhance the luminance of the pixel displayed brightest on the displayscreen and, conversely, makes it possible to suppress the luminance ofthe pixel displayed darkest. Furthermore, the findings (4) and (5) haveproved the following: When the power consumptions in the above-describedduty are made equal to each other, as compared with the case of lightingup the light-source continuously, the above-described maximum luminanceis enhanced tremendously.

Although the grounds for this phenomenon have not been elucidatedcompletely, the experimental results have clearly demonstrated thefollowing: In the pixel where the light-transmittance is set to be afixed height or more, the afterglow of the light-source in thetime-period during which the current vales is suppressed (i.e., theabove-described 2nd time-period) has maintained its luminance more thanexpected. The consideration given so far clearly proves that the presentinvention can accomplish the object and the other objects describedalready.

Incidentally, the findings (4) and (5) have been derived from the resultof a spectrum intensity obtained as follows: The panel luminancesensitivity of the liquid crystal display apparatus is measured incompliance with the conditions stipulated in ED-2522 of EIAJ (Standardsof Electronic & Mechanical Industries Association of Japan), and thespectrum intensity for each wavelength in the visible-light area (i.e.,380 nm˜780 nm) is obtained by subjecting the panel luminance to aluminous efficiency correction (i.e., converting the panel luminanceinto a light amount that the human eyes actually percept). Thismeasurement is executed under a condition that the liquid crystaldisplay apparatus is placed in a darkroom and a luminance meter is set50 cm apart from the liquid crystal display element and is locatedperpendicularly to the display region. As the luminance meter that ispreferable for executing such a measurement, there exists, e.g., thePR704 type manufactured by Photo Research Corp. This apparatus allowsthe luminance to be determined as the value of a per-unit solid anglelight-flux that does not depend on the measurement distance or themeasurement area. This apparatus also makes it possible to measure thefollowing, respectively: The integrated value of the luminance in adesired time, e.g., the above-described operation period by the amountof Δt^(I)+Δt^(II), a variation in the luminance during the time, and aluminance distribution of the liquid crystal display element within thedisplay screen. Additionally, generally speaking, the contrast ratiodescribed previously can be determined from the ratio of “a luminance atthe time when the entire display screen is white-displayed/a luminanceat the time when the entire display screen is black-displayed”. Insteadof using this general method, the contrast ratio may also be determinedin the following way:

(1) A portion of the display screen (i.e., the pixels forming an image)is caused to be white-displayed (by sending, to the pixels, animage-signal that makes the light-transmittances of the pixels theirmaximum values).

(2) A test pattern that causes another portion of the display screen(i.e., the pixels forming the image) to be black-displayed (i.e., sends,to the pixels, an image-signal that makes the light-transmittances ofthe pixels their minimum values) is displayed on the liquid crystaldisplay element.

(3) Calculating the luminance of the white-displayed portion and that ofthe black-displayed portion (at this time, the respective displayregions are assumed to be the same in size), the contrast ratio isdetermined as the luminance ratio therebetween.

In applying the present invention based on the viewpoint 1 to the liquidcrystal display apparatus, when the above-described operation period ofthe light-source is set to be smaller than the rewriting period (i.e.,16.7 ms at 60 Hz, 8.4 ms at 120 Hz) of the image data signal in theliquid crystal display apparatus, it is desirable to dispense the liquidcrystal material (i.e., the liquid crystal layer) used therein so that aresponse time of the liquid crystal material will be suppressed shorterthan the rewriting period (the above-described 16.7 ms at 60 Hz or 8.4ms at 120 Hz) of the data signal. However, if, as compared with therewriting period of the data signal, the response time of the liquidcrystal material is exceedingly slower by the amount of a predeterminedtime, there occurs a ghost phenomenon (i.e., a multiple profile). Onaccount of this, it is more desirable to shift a timing of the rewritingperiod of the image data signal from that of the above-describedoperation period of the light-source.

Consequently, it is advisable to make the two timings different byestablishing a predetermined phase difference between the operationperiod, which includes the 1st time-period Δt^(I) and the 2ndtime-period Δt^(II) illustrated in FIG. 2, and the rewriting period ofthe image data signal (i.e., the period of the synchronization signalVsync illustrated in FIG. 2).

So far, the explanation has been given regarding the modes of thepresent invention. Next, based on the following embodiments, theexplanation will be added below regarding the further details.

Embodiment 1

In the present embodiment, the sidelight type liquid crystal apparatusillustrated in FIGS. 3A and 3B is configured using the pair of glassboards 3 that are 0.7 mm thick, and a thin film transistor for the TFTdriving is formed for each pixel on one of the boards. Concerning theliquid crystal layer 2 sandwiched between the pair of boards 3, thedielectric constant anisotropy Δnε is set to be positive and Δnd is setto be 0.41 μm. Also, although the twist angle of the liquid crystalmolecules sealed in the liquid crystal layer 2 is made equal to 90°,lowering the twist angle down to, e.g., 70°, is desirable in order tomake the liquid crystal response-rate faster. In the case of suppressingthe twist angle, And that is appropriate therefor becomes even smaller(e.g., 0.35 μm), and accordingly shortening the cell gap is necessary.

The light-source unit 10 used in the present embodiment is of theconfiguration wherein, as illustrated in the perspective view in FIG.3B, the one fluorescent lamp (the cold-cathode ray tube) 8 that is 4 mmφin outer diameter is located each in the long-side direction of thelight-guiding plate 11, i.e., the two fluorescent lamps in total.Although not illustrated in the drawing here, the following componentsmay also be located: The diffusion sheet for enhancing the luminance, arecursive polarization reflection film, and a lens sheet for controllingthe angle dependence of an emitted light.

In the present embodiment, with the above-described 1st current and 2ndcurrent set to be 10 mA and 0 mA, respectively, the 1st and the 2ndcurrents are fed to the fluorescent lamps 8 with the duty of 50%. Asillustrated in FIG. 7A, the surface temperature of the fluorescent lamps8 is raised with the lapse of time. In the meantime, as illustrated inFIG. 7A, the luminance is raised with time and, after that, isattenuated temporarily, then being saturated soon.

Setting the duty to be 50% or less in this way makes the followingpossible: The temperature rises in the central portions of thefluorescent lamps 8 are suppressed down to 70° C. or less. Also, thedifference between a maximum value and a minimum value of the luminancesin the display region (i.e., effective display region) of the liquidcrystal display element (liquid crystal display panel) becomes equal tomore than 20% as large as the average value therebetween. Also, even ifthe duty is suppressed down to 50% or less, the maximum value of theluminance is made equal to 200 cd/m² or more, and the minimum value ofthe luminance is suppressed down to 2 cd/m² or less.

By the way, the lamp diameter of the fluorescent lamps used in thelight-source unit is usually about 2.6 mm, it is also possible to use a3 mm diameter type having an increased glass thickness, and a 4 mm ormore diameter type having an even thicker inner diameter and increasedcontaining quantities of the gas and the mercury. In general, the lampsurface area becomes larger as the lamp diameter is increased, which isadvantageous to the heat-dissipation. Furthermore, there also existeffects such as a lowering in the lighting-up voltage and an extensionof the lamp life-span (i.e., luminance half-value). Also, when using thecold-cathode ray tube (the fluorescent lamp) that is 2.6 mm in diameter(outer diameter), applying the tube current of 6 mA or more regardlessof the length thereof results in the heat-liberation, which lowers thelight-emission efficiency (i.e., the luminance). In contrast to this, inthe present embodiment, the outer diameter of the fluorescent lamps 8 isenlarged, thereby suppressing the influence of the heat-liberation. Thishas also enhanced a discharge efficiency by the fed current inside thefluorescent lamps, thereby making it possible to obtain a sufficientluminance even if the duty is suppressed down to 50% or lower.

In the present embodiment, using a light-dimmer circuit illustrated inFIG. 8, it is allowable to set the ratio change of the above-described1st time-period (i.e., the lighting-up time-period) or that of theabove-described 2nd time-period (i.e., the pausing time-period) duringthe above-described lighting-up period of the light-source, and thechange in the applied voltage for lighting up the lamps of thelight-source, or it is also allowable to perform these settingssimultaneously. In the light-dimmer in the lighting-up period (i.e., asillustrated in light-source luminance waveform signals in FIG. 9, thelight-dimmer based on the ratio change of the lighting-up time-period orthat of the pausing time-period), it is also possible to set theabove-described lighting-up period to be either of the lighting-uptime-period and the pausing time-period. Accordingly, as illustrated inFIG. 9, it is also possible to improve the light-emission efficiency byalways providing the pausing time-period without fully lighting up thelamps in the above-described lighting-up period of the light-source.Also, as illustrated in FIG. 10, it is also allowable to blink the lampsonly when the high luminances are obtained.

Additionally, in FIG. 9, the range of the high luminance is defined asbeing 300 cd/m² or more, the range of the immediate luminance is definedas being 200 to 299 cd/m² including 200 to 250 cd/m², and the range ofthe low luminance is defined as being 199 cd/m² or less including 100cd/m².

Embodiment 2

Next, in this embodiment, the explanation will be given below concerninga modulation lighting-up of the light-source suitable for displaying themotion-frame pictures.

In the liquid crystal display apparatus, in order to obtain motion-framepicture display characteristics that are comparable to those of the CRT,the lighting-up in the light-source is switched from the all-the-timelighting-up to the blinking lighting-up that has the lighting-uptime-period and the pausing time-period, respectively. This makes itpossible to implement the impulse type light-emission such as the CRT.At this time, as illustrated in the respective drawings in FIG. 9, it isalso possible to change the period of the blinking while maintaining thedata rewriting period (i.e., the period of Vsync here) at a constantvalue.

In this way, the impulse type light-emission comparable to the CRT canalso be implemented in the liquid crystal display apparatus using theblinking lighting-up light-source unit, thereby allowing themotion-frame picture display to be implemented. In the conventionallight-source unit, since the fluorescent lamps are always lit up (i.e.,the continuous lighting-up) regardless of whether the image-signal is ofthe bright display or the dark display, the energy efficiency has beenworsened. In contrast to this, the illumination light-quantity of thelight-source is controlled in compliance with the information amount ofthe image-signal. This enhances the light-emission efficiency of thefluorescent lamps, thereby making it possible to implement a furtherluminance enhancement based on the saving of the power consumption andthe suppression of the rise in the lamp temperature. Namely, theillumination light-quantity of the light-source is decreased when theimage is dark, and the illumination light-quantity is increased when theimage is bright. This makes it possible to control the relationshipbetween the luminance and the tone characteristic, i.e., the so-calledtone curve characteristic, in agreement with the brightness of thebackground and the image-signal. In this way, the time ratio of theabove-described 1st time-period (i.e., the lighting-up time-period) andthat of the above-described 2nd time-period (i.e., the pausingtime-period when the 2nd current is set to be 0 mA) are changed incorrespondence with the information on the bright-or-dark of theimage-signal, thereby controlling the illumination light-quantity of thelight-source.

Also, the time ratio of the lighting-up time-period and that of thepausing time-period are changed in correspondence with the informationamount about a movement of the image-signal, i.e., the lighting-uptime-period is shortened when the movement is fast, thereby allowing amore beautiful motion-frame picture display. Namely, in agreement withthe state of the image-signal, when the movement is slow, the slownessin the liquid crystal response-rate presents no problem. Accordingly,frame frequencies of input/output are made to coincide with each other,and the lighting-up time-period and the pausing time-period of thelight-source, by being made to correspond to this output framefrequency, are also controlled by the output frame period (FIG. 11A).Next, when the movement of the image-signal is faster as compared withthe above-described case, in order to improve (i.e., speed up) theliquid crystal response-rate, the output frame frequency is made 2 timesfaster than the input frame frequency so as to insert dummy data. Thelighting-up time-period and the pausing time-period of the light-source,by being made to correspond to this, are also controlled by the outputframe period (FIG. 11B).

Moreover, when the movement of the image-signal is faster as comparedwith the above-described case, the output frame frequency is made 3times faster than the input frame frequency so as to insert more amountof dummy data, thereby improving the response-rate. The lighting-uptime-period and the pausing time-period of the light-source, by beingmade to correspond to this, are also controlled by the output frameperiod (FIG. 11C).

At this time, it is advisable to perform the control so that theeffective value of the current applied to the lamps for causing thelight-source to perform the light-emission during each lighting-upperiod becomes substantially constant regardless of the ratio of theabove-described lighting-up time-period and that of the above-describedpausing time-period of the light-source. Also, changing the currenteffective value makes it possible to change the illuminationlight-quantity of the light-source. Also, by setting the luminance inthe above-described pausing time-period not to be completely 0 but to bea certain constant luminance as illustrated in FIG. 12, it is possibleto ensure a sufficient luminance even in the case where the entirescreen exhibits a high luminance. Here, it is desirable to shorten, to acertain extent, a time-period where the luminance in the pausingtime-period is enhanced.

In order to implement a more complete motion-frame picture display, itis required not only to cause the light-source unit to perform theimpulse type light-emission but also to synchronize data scanningtimings of the image-signal with timings of the blinking of thelight-source as illustrated in FIG. 16. In general, as the data scanningtimings of the image-signal, there exist a vertical or a horizontalsynchronization signal, a frame signal, a scanning line signal, and thelike. The scanning periods and the blinking periods of these signals aremade equal to each other so as to synchronize the scanning timings. Insuch a case, although the use of the directly-under type light-sourceunit is desirable and exhibits the outstanding effect, the use of thesidelight type light-source unit is also possible by the up-and-downdivision thereof.

In the up-and-down divided sidelight type light-source unit, when theabove-described period including the lighting-up time-period and thepausing time-period in the light-source is equal to the rewriting periodof the displayed image-signal, and when there exist n signal scanninglines of the above-described display apparatus, the starting time of an/2th signal scanning may be synchronized with the lighting-up startingtime of the light-source. Namely, the image-signal is synchronized withthe blinking of the light-source at the center of the screen, therebyallowing the motion-frame picture display. Furthermore, when the periodincluding the lighting-up time-period and the pausing time-period in thelight-source is equal to the rewriting period of the displayedimage-signal, and when there exist the n signal scanning lines of theabove-described display apparatus, the starting time of a n=1st signalperiod may be delayed by a certain amount of time from the lighting-upstarting time of the light-source. Here, when this delay time is set tobe the starting time of the n/2th signal scanning, the result becomesthe same as that in the method described earlier.

Also, in implementing the motion-frame picture display, it is effectiveto set the pausing time-period of the light-source to be more than1/20th as long as the lighting-up starting time, and to set theluminance in the pausing time-period to be less than 90% as high as theluminance in the lighting-up starting time.

In a liquid crystal display apparatus that includes a liquid crystalpanel including a pair of opposed-located boards at least one of whichhas electrodes and a liquid crystal layer sandwiched between the boards,a controlling circuit for applying to the above-described electrodes avoltage corresponding to a displayed image-signal, and a light-sourcefor illuminating the liquid crystal panel, the following configurationis required in order to obtain a much more beautiful motion-framepicture display: The light-source includes a lamp, a reflector forreflecting a light emitted from the lamp, and a light-guiding plate forguiding the reflected light to the liquid crystal layer, the lamp beinglocated in the length direction of at least one side of a side plane ofthe light-guiding plate, the light-source having a period including alighting-up time-period and a pausing time-period, an illuminationlight-quantity of the light-source being changed by a time ratio of thelighting-up time-period and that of the pausing time-period during theperiod and a voltage value for causing the light-source to perform thelight-emission. The light-source unit in the display apparatus isreferred to as the so-called sidelight type, and the 1 lamp is, or the 2or 3 lamps are used and located in the thickness direction. Also, inwhat position of the 4 sides of the light-guiding plate the lamp shouldbe located is determined by the luminance of the display apparatus andthe transmittances of the liquid crystal cells.

Although the 1 lamp is located along the long-side of the light-guidingplate in a high-transmittance liquid crystal such as the TN type liquidcrystal, in order to obtain a higher luminance, the 1 lamp may be eachlocated along the 2 long-sides, or the 1 lamp may be each located alongthe short-side. Besides, the lamps may not be a linearly straight-linetype but be the L-character type or the

-character type having winding points. In the IPS mode with a lowtransmittance, the 2 or 3 lamps may be each located along the 2long-sides.

In addition, in a liquid crystal display apparatus that includes aliquid crystal panel including a pair of opposed-located boards at leastone of which has electrodes and a liquid crystal layer sandwichedbetween the boards, a controlling circuit for applying to theabove-described electrodes a voltage corresponding to a displayedimage-signal, and a light-source for illuminating the liquid crystalpanel, employing the following configuration becomes required: Thelight-source includes a plurality of fluorescent lamps located directlyunder the effective display region of the liquid crystal panel, and aplurality of reflectors for reflecting lights from the respective lamps.The light-source has a period including a lighting-up time-period and apausing time-period. It is also required to change an illuminationlight-quantity of the light-source by a time ratio of the lighting-uptime-period and that of the pausing time-period during the period and avoltage value for causing the light-source to perform thelight-emission. This light-source unit is the directly-under type. Thenumber of the lamps is about 4 to 12 in the long-side direction or about4 to 20 in the short-side direction, depending on the luminance and thescreen size.

In the light-source unit, conventionally, the lamps have been locatedoutside the effective display region of the liquid crystal panel. Thisis intended to prevent the liquid crystal cells from being heated by theheat-liberation of the lamps. The liquid crystal has a property that thevalue of the refractive index is varied by the temperature change andthe transmittance is varied accordingly. On account of this, in the caseof being heated locally, its partial transmittance, i.e., the luminanceor the brightness, is varied, becoming the display unevenness. Thelight-source unit of the present invention, however, exhibits a lessheat-liberation, thus making it unlikely that such a display unevennesswill occur. Accordingly, it is possible to locate the lamps in thelight-source inside the display region as is the case with, e.g., thedirectly-under type. This also makes it possible to reduce the outerconfiguration size of the display apparatus.

As the lamps used in the light-source unit explained so far, thefollowing are available: A cold-cathode fluorescent lamp, a hot-cathodefluorescent lamp, a xenon lamp, or a vacuum fluorescent display tube.The cold-cathode fluorescent lamp has a characteristic of exhibiting aless heat-liberation. However, in order to perform the heat-dissipationmore effectively, enlarging the lamp surface area is required, and it isadvisable to set the light-source lamp diameter to be 3 mm or more.Also, setting the glass thickness of the light-source lamp to be 1 mm ormore in order to increase the heat specific-gravity results in a moreeffective heat-dissipation. It is also possible to thicken thelight-source lamp diameter and to replace an in-lamp contained gas byxenon.

Based on the explanation given so far, the concrete configurations willbe described below concerning the liquid crystal module according to thepresent invention.

FIGS. 13A and 13B illustrate an embodiment of the light-source unitwhere one fluorescent lamp 8 is each located along two long-sides of alight-guiding plate 11. FIG. 13A illustrates an inverter location whereone transformer lights up the one lamp. Instead, as illustrated in FIG.13B, the one transformer is able to light up the two lamps. In thiscase, the reduction in the component number leads to a cost saving.Here, the inverter, which is a generic term for a circuit for lightingup the lamps, includes a converting circuit for converting a directvoltage to an alternating voltage, a current controlling circuit, afrequency modulating circuit, a voltage raising current by thetransformer, and so on. Also, in addition to the transformer, the use ofa piezoelectric element is possible.

FIGS. 14A and 14B illustrate an embodiment of a liquid crystal panelincluding a transverse electric-field mode liquid crystal displayelement where a liquid crystal layer 2 has Δnd=0.28 μm and isparallel-oriented at the twist angle 0°, and an electric field parallelto the board planes is applied thereto. FIG. 14A illustrates across-sectional view of the liquid crystal display apparatus. Also, FIG.14B illustrates a perspective view of a light-source unit 10 mountedthereon. The light-source unit 10 has a sidelight type structure where2×2, i.e., 4 in total, cold-cathode ray tubes that are 4 mmφ in diameterare located in the long-side direction. Here, it is desirable that theinverter location be of a configuration where, as illustrated in FIG.15, the one transformer lights up the two fluorescent lamps 8.

Embodiment 3

In this embodiment, the explanation will be given below regarding asystem for executing a control over the blinking lighting-up of thelight-source suitable for the motion-frame picture display incorrespondence with the detection of the movement amount.

As described earlier, in the liquid crystal display apparatus, in orderto obtain the motion-frame picture display characteristics comparable tothose of the CRT, the light-source is switched from the all-the-timelighting-up to the blinking lighting-up that has the lighting-uptime-period and the pausing time-period, respectively. This makes itpossible to implement the impulse type light-emission such as the CRT.The explanation will be given below concerning the control over thisblinking.

First, consider the case where, with respect to the display region ofthe liquid crystal display apparatus, the entire display region as awhole is blinking-lit up simultaneously. Here, the explanation will begiven employing, as an example, the system using a sidelight typelight-source where one fluorescent lamp 8 is each located along twolong-sides of the display region. FIG. 17 illustrates the configurationof a controlling circuit for the sidelight type light-source, whereinthe reference numerals denote the following components: 20 an inputterminal for feeding a direct power-supply voltage from the liquidcrystal display apparatus itself, a television apparatus mounting thisthereon, or the like, 23 a light-dimmer circuit for converting thepower-supply voltage to a direct voltage equivalent to a voltage to beapplied to the light-source, 21 an inverter circuit for converting thedirect voltage to an alternating voltage, and 25 a switching controllingcircuit for controlling the time ratio of the above-described 1sttime-period (i.e., the lighting-up time-period) and that of theabove-described 2nd time-period (i.e., the pausing time-period when the2nd current is set to be 0 mA).

As described earlier, the time ratio of the 1st lighting-up luminance(i.e., the lighting-up time-period) and that of the 2nd lighting-upluminance (i.e., the pausing time-period in the present example) arechanged in correspondence with the information amount about the movementof the image-signal, thereby allowing the more beautiful motion-framepicture display. Namely, as illustrated in FIGS. 11A, 11B, and 11C, thelighting-up time-period is made shorter when the movement is fast andthe lighting-up time-period is made longer when the movement is slow, orthe lighting-up time-period is made shorter when the moving informationamount (i.e., the moving pixel number) over the entire surface of thedisplay region is large and the lighting-up time-period is made longerwhen the moving information amount is small, thereby allowing the morebeautiful motion-frame picture display. At this time, the currenteffective value applied to the lamps for causing the light-source toperform the light-emission during each lighting-up period is changed incorrespondence with the ratio of the lighting-up time-period and that ofthe pausing time-period of the light-source. This changes theillumination light-quantity of the light-source, thus making it possibleto stabilize the luminance level of the motion-frame picture display.For example, the time-period in which the 1st lighting-up luminanceoccupies the period including the 1st lighting-up luminance and the 2ndlighting-up luminance is changed in correspondence with a ratio withwhich the moving pixel number occupies the pixel number constituting thescreen of the entire display region by the display data. If, forexample, the ratio with which the moving pixel number occupies the pixelnumber constituting the entire screen by the display data is equal to10% or more over 3 frames, the display data is judged to be ofmotion-frame pictures, and the ratio of the 1st lighting-up luminance isset to be 50% or less. In the cases other than the above, the displaydata is judged to be of freeze-frame pictures, and the ratio of the 1stlighting-up luminance is set to be 50% or more.

Referring to FIG. 18, an example of the switching controlling circuit 25will be explained below. FIG. 18 illustrates the configuration of theswitching controlling circuit 25, wherein the reference numerals denotethe following components: 50 a data storing unit (which, in this case,is a frame memory) for storing display information (Data) by the amountof 1 frame and reading the information in the next frame, 52 a datacomparing unit for comparing, on the basis of the corresponding pixels,the present frame display data (Data) with the previous frame displaydata (Data′) read from the data storing unit 50, 53 a pulse controllingunit for fetching an output from the data comparing unit 52 on the basisof the amount of 1 display region (i.e., the amount of 1 frame) so as togenerate a starting time p s of the 1st time-period (i.e., thelighting-up time-period) of the light-source lighting-up signal BL and atime pw of the 1st time-period (the unit of p s and pw is assumed to bea horizontal time-period that is equal to one period of Hsync), 51 aline count unit for performing an initialization by the verticalsynchronization signal Vsync so as to count the horizontalsynchronization signal Hsync, and 54 a pulse generating unit forgenerating the light-source lighting-up signal BL by a line count valueoutputted by the line count unit 51 and p s and pw outputted by thepulse controlling unit 53. Here, the data comparing unit 52 compares, onthe basis of 1 display pixel (which is synchronized with 1 clock ofDotck), the present frame display data (Data) with the previous framedisplay data (Data′) read from the data storing unit 50. As a result ofthis, if both of the display data are different from each other, thedisplay data are judged to be of the motion-frame pictures and amotion-frame picture judgement signal is outputted toward the 1 displaypixel.

The pulse controlling unit 53 adds the motion-frame picture judgementsignals from the data comparing unit 52 by the amount of 1 screen of thedisplay region so as to cut and classify the addition result in astep-like manner, thereby distinguishing the movement information amountof the motion-frame pictures in the display region and setting thestarting time ps of the 1st time-period and the time pw of the 1sttime-period. In the data comparison between the adjacent frames, whenthe data that occupy a constant or more ratio (50% or more) with respectto the entire display region which actually displays the image data arein disagreement with each other, the moving information amount isdefined as being large. Also, when the data that occupy the constant orless ratio are in disagreement, the moving information amount is definedas being small. Incidentally, the large-or-small of the informationamount may also be defined by the comparison with a predeterminedinformation amount. Moreover, the definition of theagreement/disagreement of the data is as follows: In the comparison ofthe respective pixels, in the case of the data with constant or moretones (e.g., 128 or more tones in the case of 256 tones in total), thedata are judged to be in disagreement with each other. Also, in the caseof the data with the constant or less tones, the data are judged to bein agreement. FIG. 19 illustrates a timing diagram of the light-sourcelighting-up signal BL generated by the switching controlling circuit 25configured as described above. A notation (a) in FIG. 19 illustrates thelight-source lighting-up signal BL in the case where, as a result of thecomparison by the data comparing unit 52, almost no change has beenjudged to exist (i.e., a display close to freeze-frame pictures, asdescribe later, when comparing a pixel 1 frame previously with acorresponding pixel of input data, the amount of the disagreement isfound to be 10% or less). A notation (b) in FIG. 19 illustrates BL inthe case of a few motion-frame pictures (when comparing the pixel 1frame previously with the corresponding pixel of the input data, theamount of the disagreement is found to be in the range of 10% to 50%)(when compared with (a), more of the movement information amount existsin (b)). A notation (c) in FIG. 19 illustrates BL in the case of manymotion-frame pictures (when comparing the pixel 1 frame previously withthe corresponding pixel of the input data, the amount of thedisagreement is found to be 50% or more).

In general, the response-rate of the liquid crystal necessitates the1-frame period or more. Consequently, as illustrated in FIG. 20A, in theconventional hold type all-the-time lighting-up of the light-source, bythe time the tone attains to a reach step value to be implemented, atransition tone appears in a state of becoming a display blur. In orderto improve this display blur, the lighting-up timings based on thepulse-width and the phase of the light-source are synchronized withtimings in which the tone attains to the tone data to be reached. Thismakes it possible to suppress the display of the transition tone,thereby allowing an excellent motion-frame picture display with a lessblur.

Also, the above-described data storing units 50 are provided by theamount of a plurality of frames, thereby making it possible not only toexecute the comparison between the adjacent frame data but also toexecute the motion-frame picture detection for the time-period of theplurality of frames. This makes it possible to grasp the tendency of themovement, thus allowing a more faithful motion-frame picture judgement.

In the switching controlling circuit 25 explained so far, the framememory is provided as the data storing unit 50 so as to store thedisplay data by the amount of arbitrary frames, thereby executing thedata comparison concerning the display data by the amount of arbitraryframes and generating the light-source lighting-up signal BL incorrespondence with the comparison result. However, accompanying thedisplay region's expansion (which means the display resolution here) ofthe liquid crystal display apparatus, the memory capacity of the datastoring unit 50 is increased. When the display region was small, theswitching controlling circuit 25 could be implemented by a 1-chip ofcontrolling circuit (i.e., LSI). Because of this capacity increase,however, the switching controlling circuit 25 must become a circuit of a2-chip or more of controlling circuit configuration where the datastoring unit 50 is externally attached as the liquid crystal displayregion is expanded. This becomes a problem not only from the cost sideof the controlling circuit but also from the implementation side of theboard components. Accordingly, instead of the above-described method ofstoring the display data in the entire display region by the amount of 1frame, the data storing unit 50 may also be formed into the followingregister configuration: Data comparing pixels (i.e., detection points)have been determined in advance in the display region, and only thedisplay data on the pixels are stored. However, the total number of thepixels to be compared, which is determined by a restriction on thecontrolling circuit size, is required to be determined so that the totalnumber in the case of using the frame memory and that in the case ofbeing formed into the register configuration become substantially thesame result. Here, FIGS. 21A, 21B illustrate examples of the datacomparing pixels (i.e., the detection points). FIG. 21A illustrates thecase where the detection points are set uniformly over the displayregion of the display screen. FIG. 21B illustrates the case where thedetection points are set in a manner of being concentrated onto thecenter of the screen. In the case of FIG. 21A where the points aredistributed uniformly, the point number that becomes equal to a constantratio with respect to the entire display region which actually displaysthe display data (for example, when the constant ratio is set to be 10%,if the actual display region includes horizontal 1024 pixels×vertical768 pixels, i.e., 786432 pixels in total, the point number becomes equalto its 10%, i.e., 78643 pixels) is distributed uniformly over the actualdisplay region. Meanwhile, in the case of FIG. 21B illustrating thecentral distribution, the constant ratio point number (i.e., 78643pixels) is distributed more in the central portion than in theperipheral portion over the display region.

In the recent personal computers, the OS (i.e., operating system)employing the Windows system has become the mainstream, and thus thecomputers allow a plurality of windows to be displayed on the screen. Inaddition, since it can be considered that the window being in use atpresent is often displayed in the center of the screen, the setting ofthe detection points in FIG. 21B becomes effective.

In order to implement a more complete motion-frame picture display, itis advisable not only to cause the light-source unit to perform theimpulse type light-emission but also to synchronize the data scanningtimings of the image-signal with the timings of the blinking of thelight-source. In the present embodiment, in the center of the screen,the data scanning timings of the image-signal have been synchronizedwith the timings of the blinking of the light-source. However, being notlimited to this method, it is also advisable to determine thelighting-up starting time in correspondence with the image informationof the entire display region. Referring to FIG. 22, an example of theswitching controlling circuit 25 for implementing this method will beexplained below.

A switching controlling circuit 25 illustrated in FIG. 22 is the same asthe circuit explained in FIG. 18, except for the location of a modejudging unit 55 for dividing the display region into a plurality ofregions (e.g., dividing the display region into 4 regions as illustratedin FIG. 23) so as to judge in which region there exist many motion-framepicture displays. The data comparing unit 52 compares, on the basis of 1display pixel (which is synchronized with 1 clock of Dotck), the presentframe display data (Data) with the previous frame display data (Data′)read from the data storing unit 50. As a result of this, if both of thedisplay data are different from each other, the display data are judgedto be of the motion-frame pictures and the motion-frame picturejudgement signal is outputted toward the 1 display pixel. The modejudging unit 55, as illustrated in FIG. 23, divides the display regioninto the 4 regions and adds the motion-frame picture judgement signalsfor each region, then outputting, from this addition result, a modesignal for indicating a region where there exist the most motion-framepicture judgement signals. Next, in accordance with the mode signal, thepulse controlling unit 53 sets a starting time ps of the 1st time-periodand a time pw of the 1st time-period. FIG. 24 illustrates an example ofa timing diagram of the light-source lighting-up signal BL generated bythe switching controlling circuit 25 configured as described above. Anotation (a) in FIG. 24 illustrates the light-source lighting-up signalBL at the time of a mode Y1 where, in the uppermost portion Y1 withinthe divided display regions illustrated in FIG. 23, the mostmotion-frame pictures exist in comparison with the other 3 regions.Namely, the starting time ps of the 1st time-period and the time pw ofthe 1st time-period are set so that the 2nd time-period (i.e., thepausing time-period) will start immediately after the writing of thedisplay data in this region Y1 has been terminated (i.e., the startingtime of a n/4th signal scanning when there exist n signal scanning linesof the display apparatus).

Hereinafter, similarly, notations (b), (c) and (d) in FIG. 24 illustratethe case where the 2nd display region Y2 is in the mode, the case wherethe 3rd display region Y3 is in the mode, and the case where the 4thdisplay region Y4 is in the mode, respectively.

Next, consider the case where the display region of the liquid crystaldisplay apparatus is divided into a plurality of regions so as toblinking-light up the respective regions individually. Here, since asystem using the directly-under type light-source can be easilyimplemented, the explanation will be given below employing the system asan example. FIG. 25 illustrates the configuration of a controllingcircuit for the directly-under type light-source. Four fluorescent lamps8 are provided, and inverters 21 for controlling the lamps are eachprepared for the respective lamps, i.e., the four inverters 21 in total.The other reference numerals denote the starting components: 20 an inputterminal for feeding a direct power-supply voltage, 23 a light-dimmercircuit for converting the power-supply voltage to a direct voltageequivalent to a voltage to be applied to the light-source, and 25 aswitching controlling circuit for controlling the time ratio of theabove-described 1st time-period (i.e., the lighting-up time-period) andthat of the above-described 2nd time-period (i.e., the pausingtime-period when the 2nd current is set to be 0 mA). FIG. 26 illustratesthe configuration of the switching controlling circuit 25.

Since the directly-under type light-source is configured by the 4fluorescent lamps 8, the display region is divided into 4 regions as isthe case with the display region illustrated in FIG. 23. The switchingcontrolling circuit 25 generates and outputs light-source lighting-upsignals BL1 to BL4 for executing the control over the blinkinglighting-up of the respective fluorescent lamps 8. The data comparingunit 52 compares, on the basis of 1 display pixel (which is synchronizedwith 1 clock of Dotck), the present frame display data (Data) with theprevious frame display data (Data′) read from the data storing unit 50.As a result of this, if both of the display data are different from eachother, the display data are judged to be of the motion-frame picturesand the motion-frame picture judgement signal is outputted toward the 1display pixel. The mode judging unit 55, as illustrated in FIG. 23,divides the display region into the 4 regions and adds the motion-framepicture judgement signals for each region, then outputting, from thisaddition result, the mode signal for indicating a region where thereexist the most motion-frame picture judgement signals. The mode signaldoes not simply select and indicate the 1 region where there exist themost motion-frame picture judgement signals, but also may indicate 2 ormore regions, depending on the display. Also, in the case of indicatingthe 2 or more regions, it presents no problem whether the 2 regions areadjacent regions or dispersed regions. In addition, it is possible toeasily control the 2 regions by the large-or-small relationship in theaddition result of the per-region motion-frame picture judgement signalsoutputted from the mode judging unit 55.

Next, in accordance with the mode signal, the pulse controlling unit 53sets starting times (i.e., ps 1 to ps 4) of the 1st time-period andtimes (i.e., pw 1 to pw 4) of the 1st time-period in the light-sourcelighting-up signals BL1 to BL4 for the respective display regions. Next,the pulse generating unit 54 generates the light-source lighting-upsignals BL1 to BL4 by the line count value outputted by the line countunit 51 and ps 1 to ps 4 and pw 1 to pw 4 outputted by the pulsecontrolling unit 53. FIG. 27 illustrates an example of a timing diagramof the light-source lighting-up signals BL1 to BL4 generated by theswitching controlling circuit 25 configured as described above. Anotation (a) in FIG. 27 illustrates BL1 to BL4 in the case where thereexist a few motion-frame displays (naturally, the case of freeze-framepictures is also included) or in the case where, even if there existmotion-frame pictures to some extent, a difference in their total numbercannot be detected for each region (i.e., there exists no mode). Becausethere exists no mode, an optimum setting is performed for each region.Namely, in the region Y1, the starting time ps 1 of the 1st time-periodand the time pw 1 of the 1st time-period are set so that the 2ndtime-period will start immediately after the writing of the display datain this region Y1 has been terminated (i.e., the starting time of an/4th signal scanning when there exist n signal scanning lines of thedisplay apparatus), thereby generating the light-source lighting-upsignal BL1. Hereinafter, similarly, in the region Y2, ps 2 and pw 2 areset so that the 2nd time-period will start immediately after the writingof the display data in this region Y2 has been terminated (i.e., thestarting time of a 2n/4th signal scanning when there exist the n signalscanning lines of the display apparatus), thereby generating BL2. In theregion Y3, ps 3 and pw 3 are set so that the 2nd time-period will startimmediately after the writing of the display data in this region Y3 hasbeen terminated (i.e., the starting time of a 3n/4th signal scanningwhen there exist the n signal scanning lines of the display apparatus),thereby generating BL3. In the region Y4, ps 4 and pw 4 are set so thatthe 2nd time-period will start immediately after the writing of thedisplay data in this region Y4 has been terminated (i.e., the startingtime of a nth signal scanning when there exist the n signal scanninglines of the display apparatus), thereby generating BL4. A notation (b)in FIG. 27 illustrates BL1 to BL4 in the case where the mostmotion-frame picture judgement signals exist in the region Y1 (i.e., themode Y1). In order to optimize the motion-frame picture display in theregion Y1, the lighting-up control over the light-source is executedunder a condition that the other regions Y2 to Y4 are synchronized withthe region Y1. Namely, the starting times ps 1 to ps 4 of the 1sttime-period and the times pw 1 to pw 4 of the 1st time-period are set tobe the same value so that the 2nd time-period will start immediatelyafter the writing of the display data in the region Y1 has beenterminated (i.e., the starting time of a n/4th signal scanning whenthere exist the n signal scanning lines of the display apparatus),thereby generating the light-source lighting-up signals BL1 to BL4.Also, a notation (c) in FIG. 27 illustrates BL1 to BL4 in the case wheremany of the motion-frame picture judgement signals exist in the regionsY1 and Y2 (i.e., the modes Y1, Y2). In order to optimize themotion-frame picture displays in the regions Y1, Y2, an optimum settingis performed with respect to each of the regions, and the lighting-upcontrol over the light-source is executed under a condition that theother regions Y3, Y4 are synchronized with the regions Y1, Y2 (here, anaverage value between the optimum setting of Y1 and that of Y2 isemployed). Namely, in the region Y1, ps 1 and pw 1 are set so that the2nd time-period will start immediately after the writing of the displaydata in the region Y1 has been terminated (i.e., the starting time of an/4th signal scanning when there exist the n signal scanning lines ofthe display apparatus), thereby generating the light-source lighting-upsignal BL1. In the region Y2, ps 2 and pw 2 are set so that the 2ndtime-period will start immediately after the writing of the display datain the region Y2 has been terminated (i.e., the starting time of a2n/4th signal scanning when there exist the n signal scanning lines ofthe display apparatus), thereby generating BL2. In the regions Y3 andY4, ps 3, ps 4 and pw 3, pw 4 are set so that the 2nd time-period willstart immediately after the writing of an immediate row display data inthe region Y2 has been terminated (i.e., the starting time of a 5n/8thsignal scanning when there exist the n signal scanning lines of thedisplay apparatus), thereby generating BL3, BL4. Furthermore, a notation(d) in FIG. 27 illustrates BL1 to BL4 in the case where many of themotion-frame picture judgement signals exist in the regions Y1 and Y3(i.e., the modes Y1, Y3). In order to optimize the motion-frame picturedisplays in the regions Y1, Y3, an optimum setting is performed withrespect to each of the regions, and the lighting-up control over thelight-source is executed under a condition that the other region Y2 issynchronized with the region Y1 and the other region Y4 is synchronizedwith the region Y3. Namely, in the regions Y1 and Y2, ps 1, ps 2 and pw1, pw 2 are set so that the 2nd time-period will start immediately afterthe writing of the display data in the region Y1 has been terminated(i.e., the starting time of a n/4th signal scanning when there exist then signal scanning lines of the display apparatus), thereby generatingthe light-source lighting-up signals BL1, BL2. In the regions Y3 and Y4,ps 3, ps 4 and pw 3, pw 4 are set so that the 2nd time-period will startimmediately after the writing of an immediate line display data in theregion Y3 has been terminated (i.e., the starting time of a 3n/4thsignal scanning when there exist the n signal scanning lines of thedisplay apparatus), thereby generating BL3, BL4.

Additionally, FIG. 27 has illustrated the light-source lighting-upsignals in correspondence with the mode judging result of themotion-frame picture display. Being not limited thereto, however, itpresents no problem at all to perform the setting so that themotion-frame picture display becomes the most appropriate. Also,although the explanation has been given here regarding the method ofperforming the control in accordance with the mode judgement alone, ashaving been described earlier in FIG. 19, it presents no problem at allto set the starting times (i.e., ps 1 to ps 4) of the 1st time-periodand the times (i.e., pw 1 to pw 4) of the 1st time-period in each regionin correspondence with the total number of the motion-frame pictures.

Next, the description will be given below concerning a light-sourcelighting-up control in response to the display luminance of a displayedimage.

In the conventional light-source unit, since the fluorescent lamps arealways lit up regardless of whether the image-signal is of the brightdisplay or the dark display, the energy efficiency has been worsened. Incontrast to this, the illumination light-quantity of the light-source iscontrolled in compliance with the information amount of the image-signal(e.g., the luminance information or the like). This enhances thelight-emission efficiency of the fluorescent lamps, thereby making itpossible to implement a further luminance enhancement based on thesaving of the power consumption and the suppression of the rise in thelamp temperature. Namely, the illumination light-quantity of thelight-source is decreased when the image is dark, and the illuminationlight-quantity is increased when the image is bright. In this way, thetime ratio of the above-described 1st time-period (i.e., the lighting-uptime-period) and that of the above-described 2nd time-period (i.e., thepausing time-period when the 2nd current is set to be 0 mA) are changedin correspondence with the information on the bright-or-dark of theimage-signal, thereby making it possible to control the light-sourceillumination light-quantity. FIG. 28 is a diagram for illustrating aswitching controlling circuit 25 for performing this lighting-upcontrol. In the drawing, the reference numerals denote the followingcomponents: 56 a display luminance detecting unit for accumulating theluminance information by the amount of 1 frame from the inputted displaydata so as detect a display luminance (i.e., average luminance) levelover the entire display region, 57 a frame latch unit for latching theresult by the display luminance detecting unit 56 for a constanttime-period, 53 a pulse controlling unit that, in accordance with thedisplay luminance detection result which is the output from 57, sets astarting time ps of the 1st time-period and a time pw of the 1sttime-period in a light-source lighting-up signal for each displayregion, and 54 a pulse generating unit for generating the light-sourcelighting-up signal BL by a line count value outputted by a line countunit 51 and ps and pw outputted by the pulse controlling unit 53. FIG.29 illustrates a timing diagram of the light-source lighting-up signalBL generated by the switching controlling circuit 25 configured asdescribed above.

A notation (a) in FIG. 29 illustrates the light-source lighting-upsignal BL in the case where, as a result of the display luminancedetecting unit 56, the average luminance of the screen is found to behigh (i.e., bright). A notation (b) in FIG. 29 illustrates BL in thecase where the average luminance is found to be immediate. A notation(c) in FIG. 29 illustrates BL in the case where the average luminance isfound to be low (i.e., dark). Incidentally, when a switching is made ata high-speed between the display data with a high display luminance andthe display data with a low display luminance, if, in synchronizationwith this switching, the light-source illumination light-quantity isalso switched at a high-speed, this switching is visualized as a flickerof the display, thus becoming a problem. Accordingly, in the presentcontrolling circuit, the display luminance information latching unit 57is provided, thereby relaxing the high-speed switching of thelight-source illumination light-quantity.

Also, depending on an image displayed on the liquid crystal displayapparatus, or depending on the user's convenience, there are some caseswhere the ordinary continuous lighting-up is employed instead of theblinking lighting-up of the light-source according to the presentinvention. On account of this, it is desirable to equip theabove-described switching controlling circuit with a section forinputting a lighting-up menu selection signal from the outside. FIG. 30illustrates an example of this section. FIG. 30 is a diagram forillustrating the configuration of a lighting-up method instructingcircuit 60, wherein the reference numerals denote the followingcomponents: 61 an inputting-method judging unit for judging theinputting method of a display image-signal, 62 a lighting-up selectingunit by which the user determines whether or not to employ theabove-described blinking lighting-up of the light-source (i.e., menuselection), and 63 a lighting-up instruction signal generating unit foroutputting a lighting-up instruction signal for allowing the blinkinglighting-up to be executed in accordance with the output results from 61and 62. At present, as the display apparatuses mounting the liquidcrystal display apparatus thereon, there exist a liquid crystal monitor,a liquid crystal television, or the like. As the inputting methods ofthe display image-signal of these apparatuses, there exist an analogueRGB inputting in use for a personal computer, a composite inputting andan S image terminal inputting in use for a video monitor, acolor-difference inputting in use for a DVD player, an antenna inputtingin use for a television, or the like. On account of this, theinputting-method judging unit 61 judges what the inputting method is inview of a connection state between the inputting methods and the displayapparatuses. As the result by the inputting-method judging unit 61, ifthe inputting method is judged to be, e.g., the analogue RGB inputtingin use for a personal computer, the lighting-up instruction signalgenerating unit 63 judges that there exist a few motion-frame pictures,instructing the apparatus not to execute the blinking lighting-up of thelight-source. Meanwhile, if the inputting method is judged to be, e.g.,the inputting in use for a video monitor or a television, the unit 63judges that most of the pictures are the motion-frame pictures,instructing the apparatus to execute the blinking lighting-up of thelight-source. Additionally, assuming that these will be setautomatically, the menu selection plays a role of allowing the user tofreely select the blinking lighting-up of the light-source.

Embodiment 4

In this embodiment, the explanation will be given below concerning asystem that, in correspondence with the tone characteristic detection ofinput image data, executes a tone control and a light-source blinkinglighting-up control which are suitable for the motion-frame picturedisplay. Incidentally, the present embodiment describes, as its oneconfiguration example, a display system that the present inventor hasprototyped in order to confirm the effect actually with the use of a TFTmodule mounting an 8-lamp directly-under type backlight.

FIG. 31 is a schematic configuration diagram of the liquid crystaldisplay module according to the present invention.

In FIG. 31, the reference numerals denote the following components,respectively: 3101 a liquid crystal module, 3102 a liquid crystaldriving control board (hereinafter, referred to as “TCON board”), 3103an inverter board, 3104 a for-gate flat cable (hereinafter, referred toas “gate FPC”), 3105 a for-drain flat cable (hereinafter, referred to as“drain FPC”), 3106 an inverter controlling cable (hereinafter, referredto as “inverter cable”), 3107 a lamp high-voltage side cable, and 3108 alamp low-voltage side cable.

As illustrated in FIG. 31, the TCON board 3102 and the inverter board3103 are implemented on the back surface of the liquid crystal module3101. At first, from the system side, an image-signal and a power-supplyvoltage are fed to the TCON board 3102. The TCON board 3102 executesprocessings such as an image processing and a timing processing, thenoutputting the image-signal and a timing signal to the liquid crystalmodule 3101 through the gate FPC 3104 and the drain FPC 3105. At thesame time, the TCON board controls the inverter board 3103 through theinverter cable 3106, and lights up the lamps with a tube currentquantity fed by the lamp high-voltage side cable 3107. A back-current tothe inverter board is returned back through the lamp low-voltage sidecable 3108. Additionally, the present example illustrates thedirectly-under type liquid crystal module where the lamps are locatedwith an equal spacing therebetween on the back surface of the liquidcrystal module.

FIG. 32 is a schematic configuration diagram of the TCON boardimplemented on the back surface of the liquid crystal display moduleaccording to the present invention.

In FIG. 32, the reference numerals denote the following components,respectively: 3201 a low-voltage differential digital image-signalinputting connector unit (hereinafter, referred to as “image-signalinputting connector unit”), 3202 an image data conversion (i.e.,low-voltage differential→TTL) LSI 1, 3203 a FPGA logic data settingconnector, 3204 a FPGA logic data setting ROM, 3205 a liquid crystalpanel controlling FPGA or LSI, 3206 an operation mode setting SW of theFPGA (or the LSI) 3205, 3207 a frame memory, 3208 an oscillator, 3209 atone voltage controlling comparator, 3210 a for-gate signal connector,3211 a for-drain signal connector, 3212 variable resister for commonvoltage setting, 3213 an image data conversion (i.e., TTL→low-voltagedifferential) LSI 2, 3214 a low-voltage differential digitalimage-signal outputting connector unit (hereinafter, referred to as“image-signal outputting connector unit”), 3215 a D/A conversionconverter, 3216 an inverter control connector unit, and 3217 apower-supply circuit unit.

At first, a low-voltage differential digital image-signal from thesystem is inputted into the image-signal inputting connector unit 3201.The inputted image-signal is converted into an image-signal of the TTLformat by the image data conversion (i.e., low-voltage differential→TTL)LSI 1 3202. The image-signal after being converted is inputted into theFPGA or LSI 3205. Here, at the time of the FPGA mounting, logicalinformation that has been set in advance into the FPGA logic datasetting ROM 3204 through the FPGA logic data setting connector 3203 isread into the above-described FPGA 3205 simultaneously with thestarting-up. At the time of the LSI mounting, since a logic circuit hasbeen built in the LSI 3205 in advance, the FPGA logic data settingconnector 3203 and the FPGA logic data setting ROM 3204 becomeunnecessary (Hereinafter, in the present embodiment, the explanationwill be given employing the LSI as the example). The setting in theoperation mode setting SW 3206 controls various types of functions thatthe above-described LSI 3205 has. The above-described LSI 3205 allowsthe frame memory 3207 to be connected with the outside thereof. The useof the frame memory 3207 permits an input/output asynchronous imageprocessing to be executed. In this case, in an output-side (i.e., liquidcrystal display side) image processing, it is also possible to use aspecific clock generated by the oscillator 3208. In the image dataoutputting form from the above-described LSI 3205, there exist 2channels. The 1st channel is a channel where the image data is outputtedto the liquid crystal panel 3101 so as to drive a built-in driver ICdirectly. In this case, the image output from the LSI 3205 is outputtedto the liquid crystal panel 3101 through the for-drain signal connector3211. At the same time, the LSI 3205 outputs a gate signal to the liquidcrystal panel 3101 through the for-gate signal connector 3210. At thistime, the V-B characteristic, which is a relationship between the tonedata and the display luminance that correspond to the image outputoutputted through the for-drain signal connector 3211, is determined bythe tone voltage controlling comparator 3209 and a resistance valeassociated therewith. Also, a common voltage adjusting VR 3212 adjuststhe common voltage that becomes a reference voltage foralternately-driving the liquid crystal. The 2nd channel is a channelwhere the image data outputted from the LSI 3205 is converted by theimage data conversion (i.e., TTL→low-voltage differential) LSI 2 3213,then being outputted through the image-signal outputting connector unit3214. In the above-described 2 image data outputting forms, the displaymay be performed using the 1st channel alone. Also, the LSI 3205controls the D/A converter 3215 so as to supply an output from the D/Aconverter 3215 to the inverter board 3103 through the inverter controlconnector unit 3216, thereby executing a brightness control over thelamps. The power-supply circuit 3217 executes the generation of apower-supply voltage needed inside the TCON board 3102, one example ofwhich is as follows: With +5V voltage employed as the input, a DC/DCconverter generates the power-supply voltages of −4V, +2.5V, +3.3V, +5V,+15V, and +20V, respectively.

FIG. 33 is a schematic configuration diagram of the internal function ofthe LSIs mounted on the TCON board according to the present invention.

In FIG. 33, the reference numerals denote the following components,respectively: 3301 the low-voltage differential digital image-signal,3302 the digital image-signal converted into the TTL format by the imagedata conversion (i.e., low-voltage differential→TTL) LSI 1 3202, 3303 atiming control unit for subjecting the digital image-signal to areference timing conversion inside the LSI 3205, 3304 R, G, and B imagedata outputted by the timing control unit 3303, 3305 a reference timingsignal inside the LSI outputted similarly by the timing control unit3303, 3306 a luminance data generation controlling unit for generatingluminance data from the R, G, and B image data, 3307 the luminance dataoutputted by the luminance data generation controlling unit 3306, 3308 aluminance distribution detection controlling unit for inputting theluminance data 3307 so as to detect the luminance distribution statewithin 1 screen, 3309 the luminance distribution data outputted by theluminance distribution detection controlling unit 3308, 3310 afolded-line point tone controlling unit for inputting the R, G, and Bimage data 3304 and the luminance distribution data 3309 so as toexecute an output tone characteristic control, 3311 the output tone dataoutputted by the folded-line point tone controlling unit 3310, 3312 aframe memory controlling unit for controlling the frame memory 3207,3313 a frame memory interface signal controlled by the frame memorycontrolling unit 3312, 3314 frame memory read data read out from theframe memory 3207, 3315 an overdrive controlling unit for controlling acorrected value of the output tone data 3311 in accordance with thecomparison result with the frame memory read data 3314, 3316after-correction output tone data outputted by the overdrive controllingunit 3315, 3317 a FRC controlling unit for increasing the tone number ina pseudo manner from the after-correction output tone data 3316, 3318pseudo tone display data outputted by the FRC controlling unit 3317,3319 a driver interface controlling unit for driving the driver ICinside the liquid crystal panel 3101, 3320 a gate driver controllingsignal outputted by the driver interface controlling unit 3319, 3321 adrain driver controlling signal outputted similarly by the driverinterface controlling unit 3319, 3322 the low-voltage differentialdigital image-signal outputted by the image data conversion (i.e., TTLlow-voltage differential) LSI 2 3213, 3323 a backlight light-dimmercontrolling unit for controlling the brightness of the backlight withthe luminance distribution data 3309 employed as the reference, 3324 ablink controlling unit for controlling the lighting-up time-period andthe non-lighting-up time-period of the backlight with the luminancedistribution data 3309 and the reference timing signal 3305 inside theLSI employed as the reference, 3325 a digital backlight light-dimmersignal outputted by the backlight light-dimmer controlling unit 3323,3326 a backlight ON/OFF signal outputted by the blink controlling unit3324, 3327 an analogue backlight light-dimmer signal outputted by theD/A converter 3215, and 3328 an inverter controlling signal outputted tothe inverter board through the inverter control connector unit 3216.

At first, the digital image-signal 3302 obtained by converting thelow-voltage differential digital image-signal 3301 into the TTL formatis inputted into the timing control unit 3303. Then, the timing controlunit outputs the delay-adjusted R, G, and B image data 3304 and thereference timing signal 3305 becoming the reference inside the LSI 3205.The outputted R, G, and B image data 3304 are inputted into theluminance data generation controlling unit 3306 and the folded-linepoint tone controlling unit 3310. The luminance data generationcontrolling unit 3306 generates and outputs the luminance data 3307 fromthe inputted R, G, and B image data 3304. This luminance data isinputted into the luminance distribution detection controlling unit 3308at the next stage, and the controlling unit outputs the luminancedistribution data 3309 where the luminance data by the amount of 1 framehas been accumulated. The luminance distribution data 3309 is outputtedto the folded-line point tone controlling unit 3310 and the backlightlight-dimmer controlling unit 3323. The backlight light-dimmercontrolling unit 3323 judges a characteristic of the image data for eachframe from this luminance distribution information, thereby outputtingthe digital backlight light-dimmer signal 3325 for obtaining anexcellent display. This light-dimmer signal 3325 is inputted into theD/A converter 3215 so as to be converted into the analogue backlightlight-dimmer signal 3327, then being outputted to the inverter controlconnector unit 3216. Meanwhile, concerning the ON/OFF control over thebacklight, the blink controlling unit 3324 fetches the reference timingsignal 3305 so as to control the lighting-up time-period and thenon-lighting-up time-period during the 1-frame time-period, then, as thebacklight ON/OFF signal 3326, outputting the reference timing signal tothe inverter control connector unit 3216. The inverter control connectorunit 3216 independently outputs the analogue backlight light-dimmersignal 3327 and the backlight ON/OFF signal 3326 to the inverter controlboard 3103. In the mean time, the image data processing is as follows:The R, G, and B image data 3304 and the luminance distribution data 3309are inputted into the folded-line point tone controlling unit 3310. Thefolded-line point tone controlling unit 3310, as is the case with thebacklight control, judges the characteristic of the image data for eachframe from the luminance distribution data 3309, thereby executing foreach frame the tone characteristic (i.e., the V-B characteristic)setting for obtaining the excellent display. The tone-controlled outputtone data 3311 is inputted into the overdrive controlling unit 3315, andat the same time is written into the frame memory 3207 as the framememory interface signal 3313 through the frame memory controlling unit3312. The tone data stored into the frame memory 3207 is similarly readout by the frame memory controlling unit 3312, then being inputted intothe overdrive controlling unit 3315 as the frame memory read data 3314.Here, the output tone data 3311 turns out to become tone data 1 frameafter with respect to the frame memory read data 3314. The overdrivecontrolling unit 3315 detects a difference in the tone data betweenthese adjacent frames, then judging the movement amount of the imagedata from this difference. From this movement amount, the overdrivecontrolling unit determines, for each frame, the response-rate or theimage data corrected-value at the optimum for the luminance, therebyexecuting a correction toward the output tone data 3311. Theafter-correction output tone data 3316 outputted thereafter is inputtedinto the FRC controlling unit 3317. The FRC controlling unit generatesthe pseudo tone display data 3318 for performing a multi-tone display ina pseudo manner in a liquid crystal panel with a smaller tone number.The pseudo tone display data 3318 is inputted into the driver interfacecontrolling unit 3319 together with the reference timing signal 3305.Then, after being converted into the gate driver controlling signal 3320and the drain driver controlling signal 3321, the display data isoutputted to the liquid crystal panel 3101 through the for-gate signalconnector 3210 and the for-drain signal connector 3211. Also, as the 2ndchannel, the pseudo tone display data 3318 is directly outputted by theLSI 3205, then being outputted as the low-voltage differential digitalimage-signal 3322 through the image data conversion (i.e.,TTL→low-voltage differential) LSI 2 3213. Here, when implementing aliquid crystal module that allows the display in the configurationillustrated in FIG. 31, the above-described 2nd channel is unnecessary.TABLE 1 SW NO. function setting condition SW 1 1 light-dimmer control 1= ON, 0 = OFF ON/OFF setting 2 overdrive ON/OFF setting 1 = ON, 0 = OFF3 FRC ON/OFF setting 1 = ON, 0 = OFF 4 blink ON/OFF setting 0 = ON, 1 =OFF SW 2 1 blink duty setting 0 = 50%, 1 = 60% 2 blink phase [0] settingblink phase [2:0] = 0°˜360° delay setting 3 blink phase [1] settingequal assignment (1 step = 45° delay) 4 blink phase [2] setting SW 3 1overdrive characteristic 4 μm product Super TFT setting [0] panel 2overdrive characteristic setting [1] 3 overdrive characteristiccharacteristic setting [2] setting [3:0] = [0, 1, 1, 0] 4 overdrivecharacteristic setting [3]

Table 1 illustrates an example of the list of various types of functionsettings that are mounted on the LSI 3205 illustrated in FIG. 33 and areestablished by the operation mode setting SW 3206. The present exampleindicates the following settings: Valid/invalid settings of therespective functions of the backlight light-dimmer controlling unit3323, the overdrive controlling unit 3315, the FRC controlling unit3317, and the blink controlling unit 3324, the ratio setting of thein-1-frame lighting-up time-period at the time when the blinkcontrolling unit 3324 is valid, the phase setting of the same in-1-framelighting-up time-period, and the optimum overdrive characteristicsetting of the overdrive controlling unit 3315 in agreement with eachliquid crystal panel. In this way, the various types of functionsmounted on the LSI 3205 have been made settable independently of eachother. TABLE 2 TTL image-signal LVDS image-signal signal signal namefunction name function R[7:0] red 8-bit Y0₊/Y0_(—) low-voltagedifferential image-signal channel 0 G[7:0] green 8-bit Y1₊/Y1_(—)low-voltage differential image-signal channel 1 B[7:0] blue 8-bitY2₊/Y2_(—) low-voltage differential image-signal channel 2 DTMG imagevalid Y3₊/Y3_(—) low-voltage differential signal channel 3 VSYNCvertical synchro- CLK₊/CLK_(—) low-voltage differential nization signalchannel CLK HSYNC horizontal synchro- nization signal

Table 2 illustrates an input/output signal specification of the imagedata conversion (i.e., low-voltage differential→TTL) LSI 1 3202 and thatof the image data conversion (i.e., TTL→low-voltage differential) LSI 23213. In the image data conversion (i.e., low-voltage differential→TTL)LSI 1 3202, the input becomes the LVDS image-signals and the outputbecomes the TTL image-signals. In the image data conversion (i.e.,TTL→low-voltage differential) LSI 2 3213, the input/output becomeopposite thereto. The TTL image-signals include the respective R, G, andB 8-bit image-signals, the valid display time-period signal, thevertical synchronization signal, and the horizontal synchronizationsignal. The LVDS image-signals include the 5 pairs of low-voltagedifferential signals.

FIG. 34 illustrates a timing diagram for the signal specificationsillustrated in the above-illustrated Table 2.

In FIG. 34, a single clock constitutes the 1 pair of low-voltagedifferential signal (CLK₊/CLK⁻), and its operation frequency is equal toan input clock (CLKIN) frequency. The other 4 pairs of low-voltagedifferential signals (Y0 ₊/Y0 ⁻˜Y3 ₊/Y3 ⁻) drive the above-describedinput clock (CLKIN) frequency by 7-multiplication. The TTL image-signalstransfer the respective R, G, and B 8-bit image-signals, the displayvalid-time-period signal, the vertical synchronization signal, and thehorizontal synchronization signal. Incidentally, TI-fabricated“SN75LVDS84”, Thine-fabricated “THC63LVDF84”, or the like are availableas the image data conversion (i.e., low-voltage differential→TTL) LSI 13202. TI-fabricated “SN75LVDS83”, Thine-fabricated “THC63LVDF83”, andthe like are also available as the image data conversion (i.e.,TTL→low-voltage differential) LSI 2 3213.

FIG. 35 illustrates a schematic timing diagram of the operation of theframe memory controlling unit 3312 for controlling the frame memory3207. As the frame memory, when the resolution of the liquid crystalpanel is set to be of the XGA size, it is possible to use a 16-Mbitproduct SD_RAM. The configuration of the 16-Mbit product SD_RAM is 512KX16 bits×2 banks. Accordingly, since the data bus width is 16 bitswide, when employing the 24-bit configuration of the respective R, G,and B 8-bit image-signals, the 2 memories are used each for the writingand the reading, i.e., the 4 memories are used in total. When employinga 16-bit configuration of 5-bit R, 6-bit G, and 5-bit B image-signals,the 1 memory is used each for the writing and the reading, i.e., the 2memories are used in total. The 1 horizontal time-period of the imagedata is divided into a start-portion, an internal-portion, and anend-portion, thereby executing the command control. A full-page burstmode is employed for the access and, after setting the commands, thewriting/reading control for each pixel is executed continuously insynchronization the clock. The horizontal start-portion generates thecommands in the sequence of MRS for executing the mode setting, ACTV forexecuting a row address latch and a bank selection, and READ/WRIT forsetting the read or the write. The horizontal internal-portion generatesthe commands in the sequence of the ACTV for executing the row addresslatch and the bank selection, the READ/WRIT for setting the read or thewrite, and PRE for executing a pre-charge processing of a bank selectedby the address. The horizontal end-portion generates the commands in thesequence of WBST/RBST for stopping the full-page burst processing of theread or the write, PALL for executing the pre-charge processing of allthe banks, and REF for executing a refresh operation automatically. Theprocessing in the 1 horizontal time-period is executed by the generationof the above-mentioned commands. Concerning the vertical direction, thesame processing is repeated in a time-period during which the displayvalid-time-period signal is valid, thereby executing the image dataprocessing by the amount of 1 frame. TABLE 3 signal name main functionCL 1 data (1-line amount) latch & output signal CL 2 data fetch clockSTH data fetch start signal M alternating current converting signal FLMshift data fetch signal CL 3 data shift clock

Table 3 illustrates the function list of the gate driver controllingsignal 3320 and the drain driver controlling signal 3321. The gatedriver controlling signal 3320 includes the shift data fetch signal(FLM) and the data shift clock (CL 3). The drain driver controllingsignal 3321 includes the data (1-line amount) latch & output signal (CL1), the data fetch clock (CL 2), the data fetch start signal (STH), andthe alternating current converting signal (M), respectively. TABLE 4item symbol set value unit remark data delay tDATA 5 TPIC STH delay tSTH5 TPIC drain output timing tCL1 1040 TPIC CL 1 pulse-width tCL1W 80 TPICM set up tM 8 TPIC FLM delay tF 4 TPIC gate delay tGD 949, 857, TPIC 1.4us, 2.8 us, 767, 663 4.2 us, 5.8 us

Table 4 and FIG. 36 illustrate an example of the driver interface timingsetting specification illustrated in Table 3. The respective interfacesignals are generated from the dotclock (CK) that is the referencesignal inside the LSI 3205, a horizontal start pulse (HCLK), and ahorizontal display valid-time-period signal (HDTMG). TABLE 5 signal namemain function DACLK D/A converter control clock DACSN D/A convertercontrol chip selection signal DADATA D/A converter input digital data

Table 5 illustrates the function list of the digital backlightlight-dimmer signal 3325. The digital backlight light-dimmer signal 3325has the D/A converter control clock (DACLK), the D/A converter controlchip selection signal (DACSN), and the D/A converter input digital data(DADATA). As the D/A converter that matches this function, e.g.,“AD5300” (fabricated by Analogue Device) or the like is applicable.TABLE 6 signal name main function set value D[15]-D[14] Don't care all“0” D[13]-D[12] Mode set all “0” D[11]-D[04] Set data per-frame updatingD[03]-D[00] Don't care all “0”

Table 6 and FIG. 37 illustrate an example of the digital backlightlight-dimmer signal timing specification fitted to the AD5300(fabricated by Analogue Device). The D/A converter input digital data(DADATA) is transferred in series. The header's 2 bits (i.e.,D[15]-D[14]) mean being undefined, and the subsequent 2 bits (i.e.,D[13]-D[12]) mean a mode setting, and the further subsequent 8 bits(i.e., D[11]-D[04]) mean the data, and the remaining 4 bits (i.e.,D[03]-D[00]) mean being undefined. Here, the 2-bit (i.e., D[13]-D[12])mode setting is “all 0” which is the setting of a normal operation, andthe 8-bit (i.e., D[11]-D[04]) data is the digital backlight light-dimmersignal 3325 outputted from the backlight light-dimmer controlling unit3323 in accordance with the luminance distribution data 3309 in FIG. 33.

As having been explained so far, as illustrated in FIGS. 31 to 37 and inTables 1 to 6, the controlling circuit of the liquid crystal displayapparatus according to the present invention includes the followingcomponents that implement its main functions: The LSI, the frame memory,the low-voltage differential transferring LSIs, and the D/A converter.

Hereinafter, the detailed explanation will be given concerning the tonecontrol function and the backlight control function in compliance withthe input image data, which are mounted on the above-described LSI 3205and are the primary object of the present invention.

FIG. 38 illustrates a conceptual diagram of the operation of theabove-described luminance data generation controlling unit 3306.

In FIG. 38, in the case where the luminance data (Y) is generated fromthe R, G, and B image data, the ratios of the respective colors aregiven by the following formula (i.e., formula 1):luminance data (Y)=0.299×R(red)+0.587×G(green)+0.144×B(blue)  (formula1)

Processing this formula precisely with the hardware is difficult becauseof an increase in the circuit size, a decrease in the processing speed,and so on. Also, the luminance data generated here is the data forobtaining the characteristics of the display data. Taking this intoconsideration, the approximation processing is executed so that theluminance data can be implemented with the hardware. Since theprocessing in a pixel unit is required, it has been planned to implementthe luminance data by the shift and the addition processing. In FIG. 38,assuming that the R, G, and B image data are 8-bit digital image datarespectively, the R color is shifted by 2 bits and by 5 bits in theright direction (a 1-bit shifting in the right direction means adivision by 2, and a n-bit shifting means a division by the nth power of2), and the G color is shifted by 1 bit and by 4 bits in the rightdirection, and the B color is shifted by 3 bits, then adding all therespective shift data. This procedure allows the following approximationprocessing formula for the above-presented formula (i.e., formula 1):luminance data (Y)=0.281×R(red)+0.563×G(green)+0.125×B(blue)  (formula2)

FIG. 39 illustrates a schematic configuration diagram of the luminancedistribution detection controlling unit 3308.

In FIG. 39, the reference numerals denote the following configurationcomponents, respectively: 3901 a detection time-period setting unit forsetting a detection time-period at 1-time, 3902 an input tonedivision-number setting unit for setting a division-number of an inputentire tone region, 3903 an input image data tone region detecting unitfor detecting to which region the input image data corresponds among therespective divided tone regions set in the input tone division-numbersetting unit 3902, 3904 a 1st tone region counter for counting data in alowest tone region, 3905 a 2nd tone region counter for counting data ina 2nd-lowest tone region, 3906 a nth tone region counter for countingdata in a highest tone region, 3907 a 1st data hold latch for latchingthe total number of the data in the lowest tone region in the detectiontime-period at 1-time, 3908 a 2nd data hold latch for latching the totalnumber of the data in the 2nd-lowest tone region similarly, 3909 a nthdata hold latch for latching the total number of the data in the highesttone region similarly, 3910 a m-times multiplication circuit formultiplying, by m, a counted value by the 1st tone region counter 3904,3911 a 2*m-times multiplication circuit for multiplying, by 2*m, acounted value by the 2nd tone region counter 3905, 3912 a n*m-timesmultiplication circuit for multiplying, by n*m, a counted value by thenth tone region counter 3906, 3913 an addition circuit for adding outputdata from the respective multiplication circuits, 3914 a n*m divisioncircuit for dividing, by n*m, an output from the addition circuit 3913,and 3915 an average luminance data hold latch for latching an outputfrom the division circuit 3914 as an average luminance value.

At first, the detection time-period at 1-time is set into the detectiontime-period setting unit 3901. The output from this setting unit becomesa latch clock for a final-stage data hold latch of the respectivedetecting functions. Also, the division-number of the input entire toneregion is set into the input tone division-number setting unit 3902.Here, as an example, it is assumed that the input entire tone region isset to be 256 tones (8 bits) and the division-number is set to be 8divisions. The output from this setting unit is inputted into the inputimage data tone region detecting unit 3903. This detecting unit judgesto which region the tone value of the input image data corresponds amongthe respective divided tone regions from the input tone division-numbersetting unit 3902, then outputting a region-counting clock correspondingto the region. Here, from the setting that the input entire tone regionis of 256 tones and the division-number is 8, the tone range of eachdivided tone region becomes a 32-tone basis region. Accordingly, inorder to enhance the characteristic detection accuracy of the inputimage data, it is advisable to increase the division-number and the tonenumber of each divided tone region. The enhancement in the accuracy,however, results in an increase in the circuit size. Consequently,depending on the usage, the accuracy has been made changeable. Based onthe clock from the input image data tone region detecting unit 3903, the1st tone region counter 3904, the 2nd tone region counter 3905, and thenth tone region counter 3906 count the data numbers for each dividedtone region. During the setting time-period by the detection time-periodsetting unit 3901, the 1st data hold latch 3907, the 2nd data hold latch3908, and nth data hold latch 3909 latch the data numbers as theluminance distribution data, thereby executing the detection of theluminance distribution. The detection of the average luminance value isexecuted as follows: The respective outputs from the 1st tone regioncounter 3904, the 2nd tone region counter 3905, and the nth tone regioncounter 3906 are multiplied by the m-times multiplication circuit 3910,the 2*m-times multiplication circuit 3911, and the n*m-timesmultiplication circuit 3912, respectively. Next, the respective outputsfrom the multiplication circuits are added by the addition circuit 3913,and the output from the addition circuit is divided by the n*m divisioncircuit 3914. Finally, during the setting time-period by the detectiontime-period setting unit 3901, the output from the division circuit islatched as the average luminance data by the average luminance data holdlatch 3915, thereby executing the detection of the average luminancevalue. Here, m means the tone number within each divided tone region,and becomes equal to 32 in the present example. Consequently, whenemploying a 16-bit configuration for the respective multiplicationcircuits 3910 to 3912 and the addition circuit 3913, the division by thedivision circuit 3914 becomes a one by n*m=8*32=256. This division canbe implemented by a simple logic of the 8-bit shift processing in theright direction (i.e., the higher-order 8 bits are selected).

FIG. 40 is a state transition diagram for illustrating the operation ofa luminance distribution detecting unit in the schematic configurationdiagram of the luminance distribution detection controlling unit 3308illustrated in FIG. 39. FIG. 40 illustrates the following case used asthe one example of the explanation in FIG. 39: The input entire toneregion is set to be 256 tones (8 bits), and the division-number is setto be 8 divisions, and the resolution of the input image data is set tobe the XGA size (i.e., 1024 dots×768 lines).

In FIG. 40, the detection time-period setting unit 3901 includesvertical synchronization signals (inVsync) and display valid-time-periodsignals (inDtmg). The valid display data are displayed at the time whenthe display valid-time-period signals (inDtmg) are valid. The luminancedistribution results, which are updated on the 1-frame basis, areupdated in timings of the vertical synchronization signals (inVsync). Asthe counters (i.e., elemCntr) for accumulating the luminance data numberin the respective divided tone regions, 8 of the counters (i.e.,elemCntr00 to elemCntrO7) are prepared since the divided tone regionsare of 8 divisions. Then, the corresponding counter's value is added toa result obtained by decoding the higher-order 3 bits of the 8-bit tonedata. The accumulated 1-frame amount of luminance distribution resultsare updated (i.e., hist00 to hist07) in the timings of the verticalsynchronization signals (inVsync). Here, it is required that the size ofthe respective counters be presented assuming that the same tone dataexist by the amount of 1 frame. The present example employs the XGAresolution, which requires the counters equivalent to the amount of1024×768=786432 pixels. Namely, 20-bit counters become necessary.

FIG. 41 illustrates a schematic diagram for showing the luminancedistribution detection result obtained by the luminance distributiondetection controlling unit in accordance with FIGS. 39 and 40, and anarithmetic-calculation formula for calculating the luminance averagevalue from the detection result.

As illustrated in FIG. 41, the luminance distribution state makes itpossible to extract the per-frame light-and-shade state of the imagedata. Also, the luminance average value makes it possible to extract theper-frame screen brightness.

As another example of the state transition diagram illustrated in FIG.40 where the input entire tone region is set to be 256 tones (8 bits)and the division-number is set to be 8 divisions, FIG. 42 illustrates astate transition diagram under the following setting condition: Theinput entire tone region is set to be 256 tones (8 bits), and thedivision-number is set to be 20 divisions, and 8-divided tone regions onthe lower-order side and those on the higher-order side are set to be ofa 8-tone basis division, and 4-divided immediate tone regions are set tobe of a 32-tone basis division.

In FIG. 42, concerning the counters (i.e., elemCntr) for accumulatingthe luminance data number in the respective divided tone regions, thedivided tone regions are of 20 divisions. On account of this, 20 of thecounters (i.e., elemCntr00 to elemCntr19) are prepared. Here, in therespective 8-divided tone regions on the lower-order side and on thehigher-order side, the corresponding counter's value is added to aresult obtained by decoding the higher-order 5 bits of the 8-bit tonedata (i.e., elemCntr00 to elemCntr07, elemCntrl2 to elemCntrl9). In the4-divided immediate tone regions, the corresponding counter's value isadded to a result obtained by decoding the higher-order 3 bits of the8-bit tone data (i.e., elemCntrO8 to elemCntr11). The other controls areexecuted in much the same way as the case of the 8-divided tone regionsillustrated in FIG. 40. Namely, the accumulated 1-frame amount ofluminance distribution results are updated (i.e., hist00 to hist19) inthe timings of the vertical synchronization signals (in Vsync). Also,similarly to the previously-described case, it is required that the sizeof the respective counters be presented assuming that the same tone dataexist by the amount of 1 frame. Namely, the present example employs theXGA resolution, which requires the counters equivalent to the amount ofthe 1024×768=786432 pixels. This indicates that the 20-bit countersbecome necessary.

FIG. 43 illustrates a schematic diagram for showing the luminancedistribution detection result in the case where the tone dividingcontrol in accordance with FIG. 42 is executed, and anarithmetic-calculation formula for calculating the luminance averagevalue from the detection result.

As illustrated in FIG. 43, in comparison with the case of the 8-dividedtone regions illustrated in FIG. 41, the luminance distribution statemakes it possible to detect the distribution states of the lower-orderand the higher-order tone portions in more detail. Also, the luminanceaverage value makes it possible to extract the per-frame screenbrightness similarly to the case of the 8-divided tone regionsillustrated in FIG. 41.

FIG. 44 illustrates one example of the tone control performed by theabove-described folded-line point tone controlling unit 3310 using theluminance distribution detection results illustrated in FIG. 40 and FIG.42 at the time when the tone region is divided into the 8 regions.

In FIG. 44, in the tone control according to the folded-line pointmethod, 9 folded-line points are set on the 1-frame basis first. Next,between the adjacent points, the input tone data inputted on a1-dotclock basis is converted into output tone data in accordance with astraight-lined arithmetic-calculation formula, thereby, in real time,implementing the output tone data between the adjacent points. Here, inthe case of the equally-8-divided tone regions, anarithmetic-calculation formula of the following formula 3 can beemployed as the straight-lined arithmetic-calculation formula betweenthe adjacent points:output tone data=(rkinji(n)−rkinji(n−1))×M/32  (formula 3)

-   -   rkinji (n): higher-order side folded-line point set values    -   rkinji (n−1): lower-order side folded-line point set values    -   M: lower-order 5 bits of input tone data

Here, the folded-line points are set as an example where the luminancedistribution data illustrated in FIG. 41 is caused to be reflected so asto implement a higher picture-quality. The folded-line points are set insuch a manner as to correspond to the luminance distributionaccumulation number in each divided tone region. In this case, if thedetected luminance distribution number in each tone region is larger ascompared with an average value m (which, in the present example, isequal to a value obtained by dividing the 1-frame amount of pixel numberby 8, i.e., the number of the divided tone regions) of the luminancedistribution numbers within 1 frame, the distribution number in the toneregion is judged to be larger than the average value. Based on thisjudgement, the higher-order side folded-line points are made larger ascompared with the points (i.e., ◯ points in the drawing) at the time ofa linear characteristic. This procedure increases the dynamic range inthe tone region, thereby making it possible to obtain the excellentpicture-quality. Conversely, if the detected luminance distributionnumber in each region is smaller as compared with the average value m,the distribution number in the tone region is judged to be smaller thanthe average value, and the higher-order side folded-line points are madesmaller as compared with the points (i.e., the ◯ points in the drawing)at the time of the linear characteristic. Although this proceduredecreases the dynamic range in the tone region, it can increase thedynamic ranges in the tone regions the luminance distribution numbers ofwhich have exceeded the average value. This condition, eventually,enhances the contrasts of the regions occupying most of thedistributions as the screen as a whole, thereby allowing the excellentpicture-quality to be obtained.

FIG. 45 is a schematic configuration diagram of the folded-line pointtone controlling unit 3310 using the luminance distribution detectionresult illustrated in FIG. 44 at the time when the tone region isdivided into the 8 regions.

In FIG. 45, the reference numerals denote the following configurationcomponents: 4501 a latch circuit 1 for latching the input image data,4502 a 1-to-8 decoder circuit by the higher-order 3 bits out of outputimage data from the latch circuit 1 4501, 4503 a higher-order tone sidefolded-line point setting register/selector circuit, 4504 a lower-ordertone side folded-line point setting register/selector circuit, 4505 asubtraction circuit for subtracting a selected value by the lower-ordertone side folded-line point setting register/selector circuit 4504 froma selected value by the higher-order tone side folded-line point settingregister/selector circuit 4503, 4506 a multiplication circuit formultiplying, by an output result from the subtraction circuit 4505, avalue obtained by delaying the output from the latch circuit 1 4501 withthe use of latch circuits 2 to 5 4508 to 4511, and 4507 an additioncircuit for adding, to an output result from the multiplication circuit4506, a value obtained by delaying the output from the lower-order toneside folded-line point setting register/selector circuit 4504 with theuse of latch circuits 6, 7 4512, 4513.

The controlling circuits illustrated in FIG. 45 play a role ofimplementing the straight-lined formula between the respectivefolded-line points illustrated in FIG. 44. In the controlling circuits,the higher-order tone side folded-line point setting register/selectorcircuit 4503 and the lower-order tone side folded-line point settingregister/selector circuit 4504 set the folded-line point set valuescorresponding to the luminance distribution state (i.e., rkinji00 torkinji08) while updating the folded-line point set values on the 1-framebasis. Consequently, when the per-pixel image data (i.e., ridata [7:0])is inputted, the controlling units select 2 adjacent folded-line pointset values so as to perform the arithmetic-calculation between theselected 2 tones, then outputting the image data (i.e., rodata [7:0]).There exists an 8-clock delay from the inputting of the input image data(i.e., ridata [7:0]) to the obtaining of the output image data (i.e.,rodata [7:0]).

The present control permits an optimum tone control to be executed inharmony with the characteristics of the per-frame image data.

FIG. 46 illustrates one example of the tone control performed by thefolded-line point tone controlling unit 3310 using the luminancedistribution detection result illustrated in FIG. 43 at the time whenthe tone region is divided into the 20 regions.

In FIG. 46, in the tone control according to the folded-line pointmethod, 20 folded-line points are set on the 1-frame basis first. Next,between the adjacent points, the input tone data inputted on a1-dotclock basis is converted into output tone data in accordance with astraight-lined arithmetic-calculation formula, thereby, in real time,implementing the output tone data between the adjacent points. Here, thestraight-lined arithmetic-calculation formula between the adjacentpoints differs between the case of the equally-8-tone-basis-dividedlower-order and higher-order tone regions (i.e., hist00 to hist08,hist12 to hist19) and the case of the 32-tone-basis-divided immediatetone regions (i.e., hist08 to hist11). In the cases,arithmetic-calculation formulae of the following formulae 4, 5 can beemployed, respectively:output tone data=(rkinji(n)'1 rkinji(n−1))×M/8  (formula 4)

-   -   rkinji (n): higher-order side folded-line point set values    -   rkinji (n−1): lower-order side folded-line point set values    -   M: lower-order 3 bits of input tone data        output tone data=(rkinji(n)−rkinji(n−1))×M/32  (formula 5)    -   rkinji (n): higher-order side folded-line point set values    -   rkinji (n−1): lower-order side folded-line point set values    -   M: lower-order 5 bits of input tone data

Accordingly, as an example where the luminance distribution dataillustrated in FIG. 43 is caused to be reflected so as to implement ahigher picture-quality, performing a 2-step tone control allows theimplementation. The 1st step tone control is as follows: With respect tothe lower-order and the higher-order tone regions divided on the 8-tonebasis, the usage frequencies on the 1-frame basis are confirmed from theouter regions, respectively (i.e., hist00 in the lower-order toneregion, hist19 in the higher-order tone region), thereby determiningtone regions that can be crushed. Namely, the accumulation values arecompared with a predetermined threshold value of the tone accumulationnumbers from the outside of the respective tone regions, then crushingthe tones up to a region that has exceeded the threshold value. In thelower-order tone region in FIG. 46, since hist04 has exceeded thethreshold value n, the distribution frequencies of the tones priorthereto are judged to be smaller. Thus, 5 folded-line points from thelowest (i.e., rkinji00 to rkinji04) are set to be “0 tone”. Similarly,in the higher-order tone region, since hist17 has exceeded the thresholdvalue n, the distribution frequencies of the tones prior thereto arejudged to be smaller. Thus, 4 folded-line points from the highest (i.e.,rkinji17 to rkinji20) are set to be “255 tones”. Instead of crushing theportions existing at both of the tone ends and having the smalleraccumulation numbers, this 1st step tone control makes it possible toextend the dynamic ranges in the remaining tone regions. Also, in thepresent example, as the judging criterion for the tone regions to becrushed, the comparison with the threshold value n has been executed foreach tone region independently. An algorithm for crushing the toneregions, however, is made available in a large variety of ways by thecombination with the software processing, such as the comparison betweenthe accumulation values from the tone regions at both ends and thethreshold value n. In addition to the dynamic range's extension in theentire tone region by the 1st step, the 2nd step tone control is asfollows: As having been explained in FIG. 44, the comparison with theluminance distribution average value m is performed for eachdistribution tone region. If the comparison result is larger, thehigher-order side folded-line point set values are set to be larger ascompared with the values (i.e., ◯ points in the drawing) at the time ofthe linear characteristic so that the dynamic range in the tone regionwill be extended even further. Also, if the comparison result issmaller, the higher-order side folded-line point set values are set tobe smaller as compared with the values at the time of the linearcharacteristic so that the dynamic range in the tone region will bereduced. FIG. 46 illustrates the one example where the 2-step tonecontrol has been applied to the 32-tone-basis-divided immediate toneregions (i.e., rkinji09 to rkinji12). In FIG. 46, the extension controlregions of the dynamic ranges by the 1st step are designated ashistogram extension control regions, and the extension control region ofthe dynamic range by the 2nd step is designated as an equalize controlregion.

Also, the extension application range of the dynamic ranges by the2-step is not limited to the 32-tone-basis-divided immediate toneregions (i.e., rkinji09 to rkinji12), and the 2-step may be applied tothe 8-tone-basis-divided higher-order tone regions (i.e., rkinji04 torkinji17 in FIG. 46).

As described above, the tone controlling method illustrated in FIG. 46makes it possible to obtain an excellent display the dynamic range ofwhich has been extended even further as well as to cover the tonecontrolling method illustrated in FIG. 44.

FIG. 47 is a schematic configuration diagram of the above-describedfolded-line point tone controlling unit 3310 using the luminancedistribution detection result illustrated in FIG. 46 at the time whenthe tone region is divided into the 20 regions.

In FIG. 47, the reference numerals denote the following configurationcomponents: 4701 a latch circuit 1 for latching the input image data,4702 a 1-to-8 decoder circuit by the higher-order 3 bits out of outputimage data from the latch circuit 1 4701, 4703 a higher-order tone sidefolded-line point setting register/selector circuit for the respectivelower-order tone, immediate tone, and higher-order tone divided toneregions, 4704 a lower-order tone side folded-line point settingregister/selector circuit for the respective lower-order tone, immediatetone, and higher-order tone divided tone regions, 4705 a 3-to-1 selectorcircuit for selecting one of outputs from the higher-order tone sidefolded-line point setting register/selector circuit 4703 for therespective lower-order tone, immediate tone, and higher-order tone3-divided tone regions, 4706 a 3-to-1 selector circuit for selecting oneof outputs from the lower-order tone side folded-line point settingregister/selector circuit for the respective lower-order tone, immediatetone, and higher-order tone 3-divided tone regions, 4707 a subtractioncircuit for subtracting the selected value by the lower-order tone side3-to-1 selector circuit 4706 from the selected value by the higher-ordertone side 3-to-1 selector circuit 4705, 4708 a multiplication circuitseparated into 2 channels of the lower-order and higher-order tones andthe immediate tone for multiplying, by an output result from thesubtraction circuit 4707, a value obtained by delaying the output fromthe latch circuit 1 4701 with the use of latch circuits 2 to 6 4711 to4714, 4709 a 2-to-1 selector circuit for selecting either of outputresults from the 2-channel multiplication circuit 4708, and 4710 anaddition circuit for adding, to the output from the 2-to-1 selectorcircuit 4709, a value obtained by delaying the output from thelower-order tone side 3-to-1 selector circuit 4706 with the use of latchcircuits 7 to 9, 4716 to 4718.

As is the case with the controlling circuits illustrated in FIG. 45, thecontrolling circuits illustrated in FIG. 47 play a role of implementingthe straight-lined formula between the respective folded-line pointsillustrated in FIG. 46. In the controlling circuits, the higher-ordertone side folded-line point setting register/selector circuit 4703 andthe lower-order tone side folded-line point setting register/selectorcircuit 4704 set the folded-line point set values corresponding to theluminance distribution state (i.e., rkinji00 to rkinji20) while updatingthe folded-line point set values on the 1-frame basis. Consequently,when the per-pixel image data (i.e., ridata [7:0]) is inputted, thecontrolling units select 2 adjacent folded-line point set values so asto perform the arithmetic-calculation between the selected 2 tones, thenoutputting the image data (i.e., rodata [7:0]). There exists a 10-clockdelay from the inputting of the input image data (i.e., ridata [7:0]) tothe obtaining of the output image data (i.e., rodata [7:0]).Accordingly, the present control also permits the optimum tone controlto be executed in harmony with the characteristics of the per-frameimage data.

Next, the explanation will be given below regarding the luminancecontrol and an improving control over the motion-frame picture blur withthe use of the digital backlight light-dimmer signal 3325 and thebacklight ON/OFF signal 3326 illustrated in FIG. 33.

FIG. 48 illustrates an example of the light-dimmer characteristicdiagram in the above-described inverter board 3103. The voltage as aninput is made variable from 0 V to 3.3 V, and the duty ratio of anoutput pulse is changed in response to the voltage. Namely, the lowerthe input voltage becomes, the larger the pulse-width duty ratio becomesand conversely, the higher the input voltage becomes, the smaller thepulse-width duty ratio becomes. Since the duty ratio corresponds to theON/OFF of the backlight, the backlight becomes brighter as the voltagelevel becomes lower and conversely, the backlight becomes darker as thevoltage level becomes higher. Consequently, the digital backlightlight-dimmer signal 3325 from the above-described backlight light-dimmercontrolling unit 3323 is controlled in the scheme illustrated in Tables5, 6 and in FIG. 37, then being fed into the above-described D/Aconverter 3215. Based on the analogue backlight light-dimmer signal 3327outputted from the D/A converter 3215 in this way, the light-dimmercontrol is executed with the inverter board's characteristic illustratedin FIG. 48.

FIG. 49 illustrates an example of the luminance control and theimproving control over the motion-frame picture blur by the backlightlight-dimmer controlling unit 3323 and the blink controlling unit 3324.In the present example, the explanation will be given regarding the casewhere the light-dimmer control and the blink control are executed usingthe control signals independent of each other.

FIG. 49 is a diagram for illustrating the case where, with respect tothe continuous per-frame image data, the luminance distribution dataoutputted from the above-described luminance distribution detectioncontrolling unit 3308 are transferred in the order of a bright image→abright image→a dark image.

In general, when displaying a motion-frame picture with a liquid crystaldisplay apparatus, if the motion-frame picture is a bright image, themotion-frame picture blur phenomenon that accompanies the response-rateexceeding 1 frame becomes less conspicuous and worrying as compared withthe case of a dark image. Conversely, if, taking the motion-framepicture blur into consideration, the blink pulse-width for the brightimage is narrowed, the bright image is converted into a dark image,which, subjectively, will become conspicuous and worrying. Accordingly,the voltage level of the analogue backlight light-dimmer signal 3327 islowered for the bright image, thereby increasing the pulse-width dutyratio of the light-dimmer waveform for the backlight. Conversely, thevoltage level of the analogue backlight light-dimmer signal 3327 isheightened for the dark image, thereby decreasing the pulse-width dutyratio of the light-dimmer waveform for the backlight. Also, the presentcontrol causes the luminance distribution data to be reflected onto thenext frame detected. This is expressed by the relationship between theluminance distribution detection data and the light-dimmer waveform.Moreover, the blink control is executed in order to improve themotion-frame picture blur phenomenon resulting from the fact that theresponse-rate necessitates a time of the 1-frame time-period or more. InFIG. 49, the target is set onto a lower screen portion of the displayscreen, and the control is performed so that the blink waveform isswitched ON in the latter-half of the 1-frame time-period. Namely, inFIG. 49, assuming that the time needed for the 1-frame time-period isequal to “a” and the time during which the blink waveform is kept ON inthe latter-half of the 1-frame time-period is equal to “b”, the blinkwaveform duty ratio becomes equal to a ratio of “b:a”, which will befixed in the present example. The blink controlling unit 3324 in FIG. 33executes the present control, using the vertical reference timing signal3305 from the timing control unit 3303. The actual backlight ON/OFFwaveform turns out to become a waveform resulting from superimposing theblink waveform for the motion-frame picture blur improving control onthe light-dimmer waveform for the light-dimmer control. The liquidcrystal luminance waveform based on this waveform turns out to becomethe sloped-line portions in FIG. 49. This lengthens the light-emissiontime of the luminance waveform if the luminance distribution detectiondata is judged to be of the bright image (conversely, this shortens thelight-emission time of the luminance waveform if the luminancedistribution detection data is judged to be of the dark image). Also, itturns out that the light-emissions occur in the stationary timings ofthe liquid crystal response waveform (no light-emissions occur in thetransient timings). This condition makes it possible to obtain anexcellent display state without the motion-frame picture blur.

FIG. 50 illustrates an example of the image judgement based on theluminance distribution detection data in the example illustrated in FIG.49. FIG. 50 illustrates the luminance distribution detection data in thecase where, as illustrated in FIG. 41, the entire tone region is equallydivided into the 8 regions and the resolution of the input image data isset to be the XGA size (i.e., 1024×768). In this case, the number of thepixels by the amount of 1 frame is given by the following formula (i.e.,formula 6):1-frame total pixel number=1024 dots×768 lines=786432=C0000h  (formula6)

Here, in order to suppress the circuit size, the judgement is performedemploying only the higher-order bits of the detected data. In the caseof FIG. 50, the higher-order 8 bits are employed. The higher-order 8bits become “COh” in the hexadecimal number system, and become “192” inthe decimal number system. Consequently, the average point number in therespective equally-8-divided tone regions becomes equal to 24 points. Inthe present example, as illustrated in FIG. 50, if, as the image judgingcondition, the point numbers in the respective tone regions e, f, g, andh (i.e., 128 to 159, 160 to 191, 192 to 223, and 224 to 255 tones) areeach larger than any one of 48, 40, 32, and 24 points, the case isjudged to be of the bright image, and all the cases other than theabove-described condition are judged to be of the dark image.

FIG. 51 illustrates an example of a state transition diagram of thelight-dimmer control in accordance with the image judging condition'sexample illustrated in FIG. 50.

In the present example illustrated in FIG. 51, the light-dimmer controlis performed in a light-dimmer range ranging from a maximum luminance toa minimum luminance that is set to be 85% of the maximum luminance.Between both of the luminances, the transition is performed for eachframe in accordance with the image judging condition illustrated in FIG.50. The transition time from the maximum luminance to the minimumluminance or from the minimum luminance to the maximum luminance is setto necessitate 40 frames (i.e., about 0.67 seconds in the case where the1 frame is of 60 Hz) at the minimum. This is intended to prevent theoccurrence of a flicker. Here, the flicker occurs by the control suchthat, when the bright images and the dark images are inputtedalternately for each frame, the transition is performed between themaximum and the minimum luminances in the 1 frame. Consequently, at apoint-in-time when the image judging condition is inverted halfwayduring the transition, the transition moves in the opposite direction atthe point-in-time.

As having been described so far, the light-dimmer waveform controlillustrated in FIG. 49 is executed in accordance with the light-dimmercontrolling algorithms illustrated in FIGS. 50 and 51.

FIG. 52 illustrates another example that differs from the exampleillustrated in FIG. 49 of the luminance control and the motion-framepicture blur improving control by the backlight light-dimmer controllingunit 3323 and the blink controlling unit 3324.

In the example illustrated in FIG. 49, the final liquid crystalluminance waveform has become the waveform resulting from superimposingthe blink waveform by the blink controlling unit 3324 on thelight-dimmer waveform by the backlight light-dimmer controlling unit3323. In contrast to this, in the present example, the control over thelight-dimmer waveform by the backlight light-dimmer controlling unit3323 is not executed. Instead, the light-dimmer waveform is alwaysmaintained in the maximum luminance state, and the light-dimmer controlcorresponding to the luminance distribution detection data is executedtogether with the blink control by the blink controlling unit 3324.Namely, the control signal from the backlight light-dimmer controllingunit 3323 is controlled so that the output pulse duty always becomesequal to 100% from the light-dimmer characteristic diagram in theinverter board 3103 illustrated in FIG. 48. Next, the blink controllingunit 3324, as the example of improving the motion-frame picture blur,sets the target onto the lower screen portion of the display screen,then performing the control so that the blink waveform is switched ON inthe latter-half of the 1-frame. Moreover, the blink controlling unitmodifies the pulse-width of the blink waveform in correspondence withthe state of the luminance distribution detection data. In the examplein FIG. 52, the image data are inputted in the order of “the brightimage→the dark image→the bright image”. Consequently, the pulse-width ofthe blink waveform is widened for the bright image in the next frame,and the pulse-width of the blink waveform is narrowed for the dark imagein the next frame. Furthermore, in the example in FIG. 52, the blinkpulse-width in the backward edge of the pulse is fixed, and themodification of the blink pulse-width duty is executed in the forwardedge thereof. As a result, assuming that the time needed for the 1-frametime-period is equal to “a” and the time during which the blink waveformis kept ON in the latter-half of the 1-frame is equal to “b”, the blinkwaveform duty ratio becomes equal to a ratio of “b:a”, which is variedin correspondence with the luminance distribution detection data. Also,according to the present example, only the backlight ON/OFF controlsuffices as the interface for the inverter board 3103. Accordingly, itcan be said that the present controlling function has a generalversatility.

FIG. 53 illustrates another example that differs from the examplesillustrated in FIGS. 49 and 52 of the luminance control and themotion-frame picture blur improving control by the backlightlight-dimmer controlling unit 3323 and the blink controlling unit 3324.

In the example illustrated in FIG. 53, in contrast to the exampleillustrated in FIG. 52, concerning the modification of the blinkpulse-width duty for the blink waveform controlled in accordance withthe luminance distribution detection data, the blink pulse-width in theforward edge of the pulse is fixed, and the modification is executed inthe backward edge thereof. Namely, in FIG. 53, the blink controllingunit 3324, as the example of improving the motion-frame picture blur,sets the target onto the upper screen portion of the display screen,then performing the control so that the blink waveform is switched ON inthe former-half of the 1-frame. Moreover, the blink controlling unitmodifies the pulse-width of the blink waveform in correspondence withthe state of the luminance distribution detection data. The blinkpulse-width in the forward edge of the pulse is fixed, and themodification of the blink pulse-width duty is executed in the backwardedge thereof. As a result, as is the case with the example illustratedin FIG. 52, assuming that the time needed for the 1-frame time-period isequal to “a” and the time during which the blink waveform is kept ON inthe former-half of the 1-frame is equal to “b”, the blink waveform dutyratio becomes equal to a ratio of “b:a”, which is varied incorrespondence with the luminance distribution detection data. Also, inthe present example as well, only the backlight ON/OFF control sufficesas the interface for the inverter board 3103. Accordingly, it can besaid that the present controlling function has a general versatility.

FIG. 54 illustrates another example that differs from the examplesillustrated in FIGS. 49, 52, and 53 of the luminance control and themotion-frame picture blur improving control by the backlightlight-dimmer controlling unit 3323 and the blink controlling unit 3324.

The present example has both of the examples in FIG. 52 and in FIG. 53.Namely, in FIG. 54, the blink controlling unit 3324, as the example ofimproving the motion-frame picture blur, sets the target onto thecentral screen portion of the display screen, then performing thecontrol so that the blink waveform is switched ON in the intermediateregion of the 1-frame. Moreover, the blink controlling unit modifies thepulse-width of the blink waveform in correspondence with the state ofthe luminance distribution detection data. The modification of the blinkpulse-width duty is executed both in the forward edge of the pulse andin the backward edge thereof. As a result, as is the case with theexamples illustrated in FIGS. 52 and 53, assuming that the time neededfor the 1-frame time-period is equal to “a” and the time during whichthe blink waveform is kept ON in the intermediate region of the 1-frameis equal to “b”, the blink waveform duty ratio becomes equal to a ratioof “b:a”, which is varied in correspondence with the luminancedistribution detection data. Also, in the present example as well, onlythe backlight ON/OFF control suffices as the interface for the inverterboard 3103. Accordingly, the present controlling function has a generalversatility.

FIG. 55 illustrates another example that differs from the examplesillustrated in FIGS. 49, 52, 53, and 54 of the luminance control and themotion-frame picture blur improving control by the backlightlight-dimmer controlling unit 3323 and the blink controlling unit 3324.In the above-described respective embodiments, when focusing anattention on the improvement of the motion-frame picture blur, theaddition of the light-dimmer control has made the liquid crystalluminance waveform differ from the blink waveform. For example, in theexample illustrated in FIG. 49, an OFF time-period that accompanies thelight-dimmer control has existed in the ON pulses of the blink waveform.In the examples illustrated in FIGS. 52 to 54, the light-dimmer controlhas changed the ON pulses of the blink waveforms set in the particularpositions within a 1 screen in order to improve the motion-frame pictureblur.

The example illustrated in FIG. 55, which improves these changes in theON pulses, controls a backlight tube current as the light-dimmercontrol. Namely, concerning the improvement of the motion-frame pictureblur, as is the case with the example illustrated in FIG. 49, the targetis set onto the lower screen portion of the display screen, and thecontrol is performed so that the blink waveform is switched ON in thelatter-half of the 1-frame. Namely, in FIG. 55, assuming that the timeneeded for the 1-frame time-period is equal to “a” and the time duringwhich the blink waveform is kept ON in the latter-half of the 1-frame isequal to “b”, the blink waveform duty ratio becomes equal to a ratio of“b:a”, which will be fixed in the present example. Concerning thelight-dimmer control, if the luminance distribution detection data isjudged to be of the bright image signal, the tube current quantity forthe backlight is increased in the next frame, thereby enhancing theluminance. Also, if the luminance distribution detection data is judgedto be of the dark image signal, the tube current quantity for thebacklight is decreased in the next frame, thereby lowering theluminance. Based on the light-dimmer control by the backlight tubecurrent quantity in accordance with the luminance distribution detectiondata, the present control makes it possible to fix, in whatever cases,the blink waveform for improving the motion-frame picture blur. Thiscondition allows the stable motion-frame picture blur improving effectto be always obtained with respect to a particular region on the displayscreen.

The embodiments in the present invention allow the high-display-qualitymotion-frame picture display that exhibits the excellent light-emissionefficiency and uniformity at a high-luminance of the lamps incorrespondence with the movement speed of the image data.

Moreover, the embodiments in the present invention make it possible tochange, in real time, the dynamic range in correspondence with the tonecharacteristic of the image data. This allows the high-display-qualitymotion-frame picture display that exhibits the excellent light-emissionefficiency and uniformity at a high-luminance.

The present modes control the light-emission point-in-time ortime-period of the light-source in correspondence with the movementamount or the luminance of the displayed image. This results in aneffect of enhancing the luminance of the displayed image with ahigh-efficiency and suppressing the heat-liberation from thelight-source.

Also, the present modes control the light-emission point-in-time ortime-period of the light-source in response to the luminance of thedisplayed image and the response characteristic in the liquid crystalportion. This brings about an effect of improving the motion-framepicture blur.

Also, the present modes control the input/output tone characteristic inresponse to the luminance of the displayed image. This brings about aneffect of enhancing the contrast.

1. A display apparatus for executing display in accordance with an imagesignal, comprising: a display panel; a plurality of light-sources forilluminating the display panel; and a control circuit for controllinglight-emission luminance of the plurality of light-sources; wherein thelight-emission luminance includes a first light-emission luminance and asecond light-emission luminance, the display panel includes a pluralityof display areas, each of the display areas corresponding to each of thelight-sources, and the control circuit controls switching timing betweenthe first light-emission luminance and the second light-emissionluminance of each of the light-sources in accordance with rewritingtiming of the image signal concerned with each of the display areas. 2.A display apparatus according to claim 1, wherein the rewriting timingof the image signal corresponding to each of the display areas isdifferent from the switching timing between the first light-emissionluminance and the second light-emission luminance of each of thelight-sources and are shifted with each other.
 3. A display apparatusaccording to claim 1, wherein after a predetermined period has passedsince the image signal is rewritten corresponding to each of the displayareas, the first light-emission luminance is switched to the secondlight-emission luminance of each of the light sources.
 4. A displayapparatus according to claim 1, wherein the first light-emissionluminance is a light-out luminance and the second light-emissionluminance is a light-on luminance.
 5. A display apparatus according toclaim 1, wherein the control circuit controls the light-emissionluminance of the plurality of light sources irrespective of RGB of theimage signal.
 6. A display apparatus for executing display in accordancewith an image signal, comprising: a display panel; a plurality oflight-sources for illuminating the display panel; and a control circuitfor controlling a first light-emission luminance and a secondlight-emission luminance of each of the light-sources respectively;wherein a phase of a switching frequency between the firstlight-emitting luminance and the second light-emitting luminance of theplurality of light sources are different from one another.
 7. A displayapparatus according to claim 6, wherein a phase of switching frequencybetween the first light-emitting luminance of each of the light sourcesis different from phase of a rewriting time-period of the image signalfor display areas of the display panel which corresponds to each of thelight sources.
 8. A display apparatus according to claim 6, wherein thephase of switching frequency between the first light-emitting luminanceand the second light-emitting luminance of each of the light-sources isslower compared to a phase of a rewriting time-period of the imagesignal concerned with display areas of the display panel.
 9. A displaypanel according to claim 6, wherein the first light-emission luminanceis a light-out luminance and the second light-emission luminance is alight-on luminance.
 10. A display apparatus according to claim 6,wherein the control circuit controls the first light-emitting luminanceand the second light-emitting luminance of each of the light sourcesrespectively, irrespective of RGB of the image signal.
 11. A displayapparatus for executing display in accordance with image signal,comprising: a display panel; a plurality of light sources forilluminating the display panel; and a control circuit for controllinglight-up/light-off of each of the light-sources; wherein the displaypanel includes a plurality of display areas, each of the display areascorresponding to each of the light-sources; and wherein the controlcircuit lights up each of the light sources, after a predetermined timehas passed since the image signal is rewritten corresponding to each ofthe display areas.